Talk:Energy-efficient driving/Archive 1

Raison d'etre
This article was created by merging sections of Fuel economy in automobiles that overlapped considerably with Ecodriving, Nempimania, and Hypermiler together into a single centralized location. All three terms covered nearly identical concepts, the only significant difference between the three being where they are used. Note that some handy sources for future use may be found in the failed AfD discussion for Hypermiler, found here: Articles_for_deletion/Hypermiler MrZaius  talk  10:06, 3 June 2007 (UTC)

Content suggestion
There is a good deal of information at WikiCars that could be merged into this article to make it more complete. Dkbryant 05:10, 7 June 2007 (UTC)
 * Perhaps, but keep in mind that completeness, in this case, is defined as reaching Featured article status, rather than generating a complete list of fuel economy tips. This involves breaking down the most prominent techniques into detailed, well sourced, verifiable statements demonstrating how/why they work, who endorses/created them, etc and covering the history of the concept, preferably going back at least as far as the World Wars.   MrZaius  talk  20:46, 7 June 2007 (UTC)

...The "Fuel Selection" Section

contains completely bogus "information." It is very well established that a given gasoline engine can provide more power when it is built with a higher compression ratio, that is the combustion chamber is smaller than initially. This increases the need for higher octane fuel to prevent engine damaging knocking. The BTUs in cheap gasoline and expensive gasoline remain about 120,000 BTU per US gallon. (Ethanol has about 85,000 and Diesel Fuel is near 140,000)207.178.98.52 19:25, 6 August 2007 (UTC)

P&G / FAS Information:

I see significant problems in the descriptions of P&G and FAS.

Most importantly they are described as techniques for hybrids, whereas they are at least as useful on non-hybrids if not more so. Implementation is a bit different for a hybrid as you need to trick the car in to disengaging both the internal combustion engine and hopefully also the electrical charge/discharge activity. For a conventional car you just put it in neutral and either shut off the engine or not.

As P&G vs. FAS are essentially the same we need to show that. However the basic concept needs to be spelled out much more clearly than it is.

Also P&G / FAS should be detailed with more specific information for use with hybrids, and for conventional vehicles with standard or auto transmissions as the application will vary.

I think I could write something better than what we have now but I'm still a noob here at Wikipedia.

Within this discussion I'd like to reference the post below (not by me). It's significant in that it shows clearly the value of pulse & glide vs. steady state speed. http://www.cleanmpg.com/forums/fuel-economy/t-very-preliminary-non-hybrid-sgii-results-pg-speed-effects-accel-climbing-4819.html

Comments?

Brucepick 12:10, 9 June 2007 (UTC)
 * The content we have now was from a couple of articles that were advertisement-like in tone, hyping hypermiling and ecodriving, and a clunky two or three paragraph section-stub at the main fuel economy article.  Feel free to completely rewrite this article, if you think you can do so without sacrificing any valid information, but please keep in mind that the goal, as stated above, is creating a strong encyclopedia article, not a howto guide or book on maximizing fuel economy - For that, you'd be better off looking at the wikicars site mentioned above or wikibooks. It seems to me that we need most desperately is thoroughly cited, verifiable coverage of who recommends what and why.  MrZaius  talk  16:02, 9 June 2007 (UTC)

Flora_Poste 12:51, 21 August 2007
 * I agree more or less with Brucepick: I think that what is most needed on this page is a well referenced list of the various eco-driving techniques that have been proposed and investigated, with quantification of the impact of each technique. There is validity in describing types of eco-drivers as a secondary topic. Discussion of hybrid cars belongs elsewhere, as eco-driving is about the style of driving, and car maintainance - not the car. 12:51, 21 August 2007

P&G seemed inaccurate to me, inasmuch as it strongly implied that the technique only works for some hybrids, whereas the technique predates hybrids, so I rewrote it. It's not perfect, there's a lot more information I don't have the time to track down (references to P&G being utilized as early as the 1950s, ideal speed ranges, etc - perhaps this should eventually get its own article, I don't know, I'm a bit of a noob wiki editor), but it's better than what was there by a fair amount. Ravaet (talk) 10:07, 30 December 2007 (UTC)

Slight problem with interpretation of fig 5-7
Modeling Light-Duty Vehicle Emissions Based on Instantaneous Speed and Acceleration Levels, [4], kyoungho Ahn, 2002 Virginia Tech PhD Thesis, Fig. 5-7

Is a great reference but we somehow need to make clear that although the fuel consumption at a given speed increases as the acceleration is increased, this may or may not be more efficient - more work is being done as the vehicle gains more KE per second.

While I'm at it, you'll normally see worse fuel economy overall if you acccelerate harder up to the same target speed, what you really need to do is to accelerate harder to a lower target speed, to maintain the same average speed. Greg Locock (talk) 01:05, 22 January 2008 (UTC)


 * I was referencing it just for the 0 acceleration case. Maybe I should add more explanation in the footnote.Ccrrccrr (talk) 01:45, 22 January 2008 (UTC)

Source problem
I'm seeing a number of sources listed there which are blogs or other self-published sources. These don't meet WP:V and need to be cleaned up and replaced by reliable sources.--Crossmr (talk) 14:27, 8 February 2008 (UTC)

Fuel Choice is Irrelevent
Currently the article reads:
 * The efficiency of a gasoline engine is related to the fuel's octane level. Differences in cleaning agents between brands of fuel and between loads of unbranded fuel can also have a noticeable impact Citation needed. Drivers may also weigh the fuel efficiency of multiple fuels for flexfuel vehicles and diesel vehicles, as the use of biofuel can result in marked changes in fuel economy in the same engine Citation needed.

A car requires the type of gasoline it was designed for, choosing a fuel for its octane content is unrelated to maximizing fuel economy. A high compression engine needs high octane fuel to prevent detonation. A lower compression engine doesn't, and giving it higher octane fuel is a waste.

I find the claim that differences in fuel cleaning agents actually has a noticeable affect on fuel economy unlikely, but I have no support. Gasoline is generally all taken from the same pipe, where distributors pick up a load and add chemical gimmicks designed to differentiate the brand... LostCause 04:08, 26 August 2007 (UTC)

Speaking only from experience, I ran several tanks of each grade of fuel through my Geo Tracker, and found I had the best mileage with mid-grade (89 octane) gas, good enough that it countered the slightly higher price. My theory is that lower grade gas causes the motor to ping slightly, so the computer advances the ignition timing, which is slightly less efficient. I would advise others to do the same thing, test each grade of gas in their car, rather than taking it on faith that one grade or another is the right one. —Preceding unsigned comment added by

Currently, the article reads:-

"It is commonly believed that efficiency of a gasoline engine is related to the fuel's octane level; however, this is not true in most situations. Octane rating is only a measure of the fuel's propensity to cause an engine to "ping"; this ping is due to "pre-combustion", which occurs when the fuel burns too rapidly (before the piston reaches top dead center)."

This is incorrect. "Pinging" refers to detonation, i.e. explosive combustion, and the octane rating is a relative index of the fuels tendency to detonate. The phenomena described here is pre-ignition, a different, and generally more damaging, malfunction. The octane rating influences the fuels tendency to pre-ignite, but it is not defined by it.

These terms are very widely mis-used.

64.65.77.28 (talk) 06:55, 12 March 2008 (UTC)

Recent reverts
I don't want to be getting into a revert war here, but the 01:47, 26 March 2008 version by Mikiemike seems to be in error. It has the content and figure in Fuel_economy-maximizing_behaviors repeated twice. It was made on the basis of restoring my "unexplained and unsummarized deletions" but if you look at the page history, my edits do have summaries and the deletions are explained as moving material. If you don't like my reorganization, please explain why not, and move the material back, rather than having it repeated.

What we might need to discuss here is the safety section, which was deleted on the grounds that it was original research. That seems true to me--if it's not original research, the burden of proof is on somebody who claims it's not to provide sources. Ccrrccrr (talk) 03:12, 26 March 2008 (UTC)


 * Ccrrccrr, your entire edit summary just states: 'deleting section moved below', without saying what section you're referring to, or why it was deleted. --Mikiemike (talk) 15:22, 27 March 2008 (UTC)


 * I deleted the safety section because it was not sourced. I know that normally you just tag this things, but if you read that section, it seems to attempt to convince the reader to try out turning off the engine while driving which is a terrible idea.  Brusegadi (talk) 03:33, 26 March 2008 (UTC)

'''The goal here is to give people all the info, so they can reach their own conclusion. It's not your job to censor information.''' To censor info is just as manipulative as trying to convince someone of something with biased info. If you think the language is an 'attempt to convince', then the language can be improved. Anyway, there are numerous factors that influence safety. Some are subtle, others are not so subtle. Arriving at a reasonable conclusion requires all the facts, and a study of the issue, and those conclusions should be left for the reader to decide for themselves, and not left to the editors (like you or me) to decide. The safety of these behaviors are obviously an important issue. You yourself say that it's a 'terrible idea', and you use that as a reason to not engage in those behaviors, therefore this is a good reason to cover the issue in the article. You had the opportunity to explain why turning the engine off might be unsafe, but you missed your chance when you allowed the entire section on safety to be deleted. Currently all the readers are left in the dark about all the safety advantages and disadvantages of these behaviors. So can we get a vote on this?  Who thinks a section on the safety issues should be in the article, if the material is referenced?
 * Maybe half the material on Wikipedia is unsourced. Are you going to delete half of Wikipedia too?  You know, it's sometimes better to source it rather than start over from scratch.  Turning the engine off is not a concept that I made up.  There are a lot of websites that talk about people who use this "Fuel economy-maximizing behavior".  Apparently they survived to write their webpage, so apparently it doesn't have the 100% suicidal rate you claim, a conclusion which is based on your original research!  Anyway, because there are sources that say people turn the engine off, that makes it relevant to the article, and it doesn't matter whether you think the behavior is a good idea or not.  I'm not completely biased, because I did mentioned the reasons I found in my research why it may be unsafe.  Are you going to delete the article on suicide too, because you don't think it's a good idea and you don't want to risk convincing someone that it's a good idea?  No, of course not!  You would re-word it, not delete it.  So to use as a criteria for deletion is seriously flawed.


 * The article got messed-up when people simultaneously moved sections and then deleted them, without explanation or discussion, plus made other edits at the same time. All I did was click, and that should not have caused duplicate material unless somebody did copy-and-paste on a section, instead of cut-and-paste.

(See also this discussion: User_talk:Mikiemike)

Mikiemike (talk) 15:22, 27 March 2008 (UTC) There are plenty of subjects that are real, particularly in pop culture, which can be difficult to find reliable sources for, and there are plenty of subjects that are established in practice, but which are rarely written about in what you call "respectable sources". Coasting in neutral is not a new idea. I listed some sourced facts, and you deleted them all. I see nothing wrong in with adding relevant information that is reliably sourced. Controversial topics inevitably become just a list of facts. There's a difference between listing the facts, and WP:SYN which has to do with drawing original conclusions. If you think I'm drawing an original conclusion, then mention that here, or delete that statement only, rather than deleting the entire section, the rest of which is legitimate. This is not a "how to" manual for driving any more than the suicide article is a how-to manual! Rather, Wikipedia consists of articles that covers all the issues within each subject, whether recommended or not. Also, blogs are part of pop culture, so there needs to be a distinction between referencing pop culture and referencing what you call "established" practice. The only reference in my recent addition that might be construed as a blog, is cited as an individual account of hypermiling, tailgating and road rage. What's wrong with that? Even legitimate sources use information that is based on talking to the man in the street. WP says that material doesn't have to be pure truth, which is impossible to determine anyway, it just has to be "verifiable". Anyway you deleted all of my credible references. Are you a discriminating "editor" or a non-discriminating "deleter"?
 * Then please bring in the reliable sources that discuss this technique, I ma sure that the article on suicide has many since it is a practiced studied in many fields, on the other hand, your drivign technique seems to be right out of Joe's blog. Furthermore, other stuff exists is not an argument; yes, there is much stuff in wikipedia that is not cited and we keep it because we have not enough labor to remove it.  Really, some articles read like the insane are running the asylum.  So, since the technique sounds fringe (I could not find any mention of it in respectable sources), I will not tag it, I will just remove it since wikipedia is not a vehicle to spread new ideas, it is a vehicle to explain established ones. Brusegadi (talk) 16:58, 27 March 2008 (UTC)
 * Brusegadi,

Mikiemike (talk) 20:38, 28 March 2008 (UTC)-- An example of WP:SYN would be to say that coasting in neutral on frozen roads is okay, so it's safe to drive in neutral all the time. This is not what I said. I think you (Brusegadi) jumped to this conclusion, and assumed that I was implying that. Obviously there are similarities and differences. But to simply say that coasting in neutral is illegal and should never be done isn't telling the whole story. So it wouldn't be right to delete that either. Instead of deleting it, improve on it, or suggest something better. --Mikiemike (talk) 18:35, 29 March 2008 (UTC)
 * You are attemting to legitimize your edits by quoting government sites that are about driving in frozen roads, thats WP:SYN. You seem to not get this and I think that you also think I have somethign against you, so I will ask for a third opinion. Brusegadi (talk) 21:10, 28 March 2008 (UTC)
 * The things you say about what I am "attempting" to do is your perception and opinion. You're entitled to that, but WP is another matter.  Some people say driving in neutral is totally illegal and totally unsafe and should never be used.  Other people say they do it all the time and it's not that dangerous.  So the issue is what should the editors do about this controversy?  What I've done is in between these two extremes.  I've said: on the one hand it's illegal and can be unsafe in some circumstances, while on the other hand there are instances when it is legal to drive in neutral and it is considered safe.  If that is not balanced enough for you, then help make it more balanced.  I strongly disagree with anyone who thinks that censoring a POV resolves the controversy.  I reject that mentality completely.


 * I think we are moving in a good direction, it is easier to source "driving in neutral" than "driving with the engine turned off." I really like saving fuel, but I dont like when people say wikipedia is not reliable.  This happens when editors slack off and are not serious about their sources.  Hence, we both can know something, but we still need to source it.  Thats all I am saying, just abide to WP:RS and WP:OR.  I will try to find a serious website that discusses the dangers of this, and if everything is credible, I think it should be fine.  Brusegadi (talk) 21:23, 29 March 2008 (UTC)


 * Brusegadi, One or more of the references for Wyane Gerdes says that he does "auto-stop" maneuvers (i.e. with the engine off). WP:SYN says to "stick to the sources". --Mikiemike (talk) 19:24, 30 March 2008 (UTC)
 * Yes, and that is not a good source for the technique in general, it is a good source for Gerdes liking that stuff thought. This is not mainstream, as your unability to find a good source demonstrates, so it is getting undue weight compared to more mainstream practices. Brusegadi (talk) 19:31, 30 March 2008 (UTC)


 * I think you both have good points here. I think the best solution is to include some of this material, carefully edited, rather than stripping it out completely or including it all.  This is not the place for a long, rambling collection of all the ideas anyone has had about this stuff.  A more extended discussion, with more of a how-to focus might be appropriate in wikibooks, and could be linked from here.  In approaching a compromise through multiple edits, we may improve the quality of the writing, as well as reaching a good balance as far as what material is included.Ccrrccrr (talk) 13:10, 29 March 2008 (UTC)

--Mikiemike (talk) 18:35, 29 March 2008 (UTC)
 * Crrccrr, I agree. However, the article isn't that long yet, even to be a complete article, let alone a book.  Anyway, organization matters more than length.  A longer organized article is better than a shorter unorganized article.  The issue is, can the reader quickly find the info they're looking for.  IMHO, the safety issues of driving in neutral qualifies as an FAQ.  So IMHO a section on this is appropriate.  I think it's so ironic that you guys want to delete the safety section due to reasons of safety.  Ironically the very reason why you guys want to delete it is the reason why it's an important and relevant issue.  Anyway, there are credible references that professionals like Wyane Gerdes use these controversial maneuvers, and this makes it "established", and not WP:Fringe, despite Brusegadi's claims.  Maybe you guys should find some valid sources to back up your claims that these maneuvers are unsafe, rather than just deleting sourced info based on your suspicions.  Deleting sourced material is like "reverse-vandalism".

Additions to "Fuel economy-maximizing behaviors" article
Dear editors, we are trying to source all the material for this article, because the topics are controversial. Please include sources or else unreferenced additions may be deleted. Thanks, --Mikiemike (talk) 20:46, 12 April 2008 (UTC)


 * Actually, I tried to post the source of my recent addition to the article on "drafting", but for some reason Wikipedia won't allow the site to be posted as a reference, I get a message that the site has been "blacklisted". I cannot even post the URL here, but it is one of the articles at "omninerd dot com".  Can anyone shed some light about what is going on here? SONORAMA (talk) 09:58, 13 April 2008 (UTC)

Deleted unsourced "Drafting or tailgating" section by User:SONORAMA 15:55, April 12, 2008
I just removed the following material. It sorta sounds good, but it is unsourced. Due to the controversial subject, the defacto policy is to delete all unsourced material. (I had to put up with it, so everyone else does too.) User was warned above and on their talk page.

User:SONORAMA 15:55, April 12, 2008 wrote:
 * ";Drafting or tailgating. Following a large vehicle such as a semi-tractor trailer on the highway will increase fuel mileage due to the reduction of air resistance.  However, this is only accomplished with great risk. Should the truck suddenly apply the brakes, a rear-end collision could ensue.  Furthermore, any savings in gas mileage would likely be spent on repairing windshield damage from stones or other debris kicked up by the truck.  The drafting driver's visibility is also greatly diminished, thus the driver is unable to avoid small road obstacles such as tire re-treadings."

--Mikiemike (talk) 02:52, 26 April 2008 (UTC)

Removed unsourced material
I just removed this passage:
 * "Coasting in neutral removes one control drivers might otherwise use to avoid accidents: acceleration; leaving only braking and steering controls. Thus, advocates of coasting may discount the likelihood that acceleration (lost when coasting in neutral) is critical for avoiding most accident scenarios."

At first the language confused me. After re-reading it I understood it, but this subject is so hyper-controversial, and so difficult to keep neutral. We really need references.

I agree that "Coasting in neutral reduces the driver's control of the vehicle to an extent." However, it is controversial and uncertain whether drivers might otherwise use acceleration to avoid accidents, and whether this is more safe than using only braking and steering controls. I somewhat agree that "advocates of coasting may discount the likelihood that acceleration (lost when coasting in neutral) is critical for avoiding most accident scenarios."; however it is equally valid to say that "critics of coasting may overstate the significance or importance of acceleration for avoiding accident scenarios.". Neither statement is really neutral. Anyway, Wikipedia technically requires everything to be referenced. Neither of these statements is supported with references. --Mikiemike (talk) 07:30, 1 May 2008 (UTC)


 * I don't think it is controversial, as such. Nobody who understands the implications would deny that coasting in neutral is somewhat less safe than being in gear, and either are preferable to switching the engine off. Whilst this may be inconvenient to someone's argument, I doubt you will find any rational person who claims different. If some enthusiasts believe that the increased risk is justified by the fuel consumption saving, you may be able to find quotes supporting that. I doubt they will be WP:RS. The reasons why coasting in neutral is less safe is not just that the option of accelerating out of trouble is removed. That's actually less important than some other reasons. I'll have another look through this appalling article and see if it bears some weeding.Greg Locock (talk) 08:50, 1 May 2008 (UTC)


 * There has been a history of additions and reverts on this topic, and much discussion, and by definition that proves it is controversial.

You wrote: "Nobody who understands the implications would deny...". I disagree with that reasoning. You don't speak for everyone, and you don't speak for me. I have a different POV. We need to acknowledge and respect each other's POV. Wikipedia policy includes: WP:NPOV, WP:RS. Any unreferenced content can be removed, period. Referenced content should not be removed until it is discussed, and the dispute is resolved. There are multiple points of view on this subject, and they all should be represented in the article. Just because you don't agree with some of the content is not a valid reason to remove referenced content, because this content may represent a POV other than your own. I assure you that these behaviors, while they are controversial, are practiced by recognized and celebrated practitioners, and there are reliable sources and verifiable sources to support these claims. If you read the article and check the references, I'm sure you will find this is the case. It may seem strange to you, but WP says that verifiability is more important than "truth". "Truth" is subjective, but verifiability is objective. There is a certain truth in verifiability. Wikipedia is criticized for allowing anyone to write whatever they want. Verifiable references are the solution to this problem. Also, nothing I know of resolves controversy faster than allowing multiple POV's, and using neutral unbiased language. --Mikiemike (talk) 00:46, 2 May 2008 (UTC)

I suggets that you read what I wrote as opposed to what you seem to think I have written. Greg Locock (talk) 05:31, 2 May 2008 (UTC)

First para crit
"Fuel economy-maximizing behaviors describe techniques that drivers can use to optimize their automobile fuel economy. The energy in fuel consumed in driving is lost in many ways, including engine inefficiency, aerodynamic drag, rolling friction, potential energy required to climb hills, and kinetic energy lost to braking (absent regenerative braking). Driver behavior can influence all of these." So, these cars climb hills, but never descend them. Somehow the driver can choose not to ascend hills, what does he do, build a tunnel? Bit tough if he lives at the top of the hill.

"The city mileage of conventional cars is much lower than highway mileage due to: 1) a high proportion of idling time, 2) operation mostly at very inefficient low-output engine operating points, and 3) more frequent braking." eg Nissan sentra auto 29 mpg city 36 highway. Is that really MUCH lower?

Greg Locock (talk) 09:49, 1 May 2008 (UTC)


 * Potential energy from climbing hills is recovered when decending. see conservative force.   Any car that ascends a hill will eventually descend.
 * 29 mpg is 20% lower than 36. This is significant, especially with climate change being what it is, and when most vehicles run on non-renewable fuels.  Also prices are at record levels.  It is significant difference when a hybrid vehicle or electric vehicle can get 50 to 100 mpg city.
 * --Mikiemike (talk) 00:46, 2 May 2008 (UTC)


 * way to go missing the point again. Ah well, I shall enjoy editing this article. Greg Locock (talk) 05:32, 2 May 2008 (UTC)

Fuel Economy infobox
In a related matter, does anyone think that fuel economy should be kept out of the automobile infoboxes? Please voice your opinion at http://en.wikipedia.org/wiki/Template_talk:Infobox_Automobile#Vote_on_Fuel_Economy_in_the_Infobox 198.151.13.8 (talk) 18:28, 7 May 2008 (UTC)

Vehicle Choice Section
"Selecting a more efficient vehicle type such as a bicycle, public transport or even walking, all of which use much less fuel per passenger mile than private automobiles."

Since this article seems to be addressing how to improve fuel economy of a given vehicle, this section seems out of place. Walking will obviously use less fuel than driving, but that has nothing to do with fuel economy.

Zachen3 (talk) 18:01, 3 June 2008 (UTC)


 * Will it?? How much fuel (as in food) would five people need to consume to walk 100 miles safely? At current US prices it would cost about $13 in a 30mpg vehicle, less in one that consumes less. What would be the cost of food for 5 people, keeping in mind that they should be healthy at the end and not starving/losing weight. --Bob (talk) 19:51, 12 June 2008 (UTC)

Driving Barefoot
Ok, this qote is from the article: "Nempimania (also Nenpimania) is an obsession with getting the best fuel economy possible from a hybrid car. It is derived from the Japanese "nempi" (燃費)--a contraction of nenryōshōhiryō （燃料消費量）[4] meaning fuel economy, and mania, meaning "craze for." Nempimania is exhibited by owners of the Toyota Prius and other hybrid owners by various habits aimed at maximizing fuel economy: slow starts, "Pulse and Glide", timing stoplights, driving barefoot, etc. "

I seriously doubt driving barefoot has anything to do with fuel economey or Toyota Prius or any other Hybrid drivers in general.12.152.160.239 (talk) 18:32, 3 June 2008 (UTC)


 * you feel the accelerator more, are more sensitive to it, so you push it less. 'tis known --Bob (talk) 19:58, 12 June 2008 (UTC)

Factually Inaccurate
When accelerating, the engine should be kept in the peak of the torque curve, this is usually at around 75% throttle Citation needed. A slow acceleration is less efficient.

This is completely wrong, in terms of fuel economy. The maximal fuel economy is achieved at a fairly slow rate of acceleration. The car should be in its efficient powerband (RPMs not too low, not too high) but there's no reason to suggest that a certain throttle position is optimal for all cars.


 * Actually, the quoted statement is correct. This long report includes an engine efficiency map; if you look at other they are broadly similar.  Efficiency varies weakly between about 50% and 100% throttle; below 50% throttle it drops rapidly.Ccrrccrr (talk) 14:01, 19 January 2008 (UTC)

Actually, that statement is just too ambiguous, and is both correct and incorrect. Yes, Engine efficiency is more efficient at full throttle, but overall efficiency is not. Engines are also more efficient around 5500 RPM, but they aren't operated at that rate because of frictional gear losses. Optimal efficiency is realized with gradual acceleration from a rolling start.208.181.244.18 (talk) 21:28, 30 June 2008 (UTC)Omid

Optimal efficiency can be expected while cruising with no stops, at minimal throttle and with the transmission in the highest gear. For most cars these conditions are satisfied at a speed of approximately 35 miles per hour.

Also wrong, the EPA has published data that shows peak efficiency is somewhere around 55-60mph for most cars. This is the point at which air resistance begins to become a significant factor.

It's not saying that 35 mph is the peak efficiency, but the point of near peak efficiency. Between 35 and 60 mph, you don't have much better efficiency. 208.181.244.18 (talk) 21:30, 30 June 2008 (UTC)Omid

These are just a couple examples, but the whole article is full of unsupported and highly questionable claims to anyone with a basic knowledge of physics. Suggest the article be rewritten or simply taken down, in its current form its only function is to misinform. Crouchingturbo 20:26, 23 August 2007 (UTC)


 * The link above to EPA "published data" is not really data, at least not that I could find. If you dig deeper and read EPA testimony on speed limit laws, they admit that their data isn't really very useful for that.  So let's try to find some actual data.  Here's one data set.Ccrrccrr (talk) 05:22, 19 January 2008 (UTC)


 * Here's information on the factor used in California models, but that's not ideal, since it's over a whole cycle, not a steady speedCcrrccrr (talk) 05:26, 19 January 2008 (UTC)


 * Here's a PhD thesis that uses data collected from a large assortment of vehicles to build a model. It includes graphs comparing data to the model. The data in Fig. 5-7 shows that fuel economy varies little in the 35-to-55 mph range, gets worse quickly above 60.  (Considering the upper right plot, which is for zero acceleration.)  MODELING LIGHT DUTY VEHICLE EMISSIONS BASED ON INSTANTANEOUS SPEED AND ACCELERATION LEVELS, kyoungho Ahn, 2002.  —Preceding unsigned comment added by Ccrrccrr (talk • contribs) 13:52, 19 January 2008 (UTC)

Citation Needed For Loss of Control While Motor Is Powered Off
Additionally, I have deleted the "Citation Needed" tag from the bottom of the "Safety" heading, after the last line. I don't know what kind of witless nincompoop would claim that the inability to accelerate, use power steering, employ ABS, or brake for prolonged periods without the lines losing pressure isn't going to lower the effective control of their vehicle (and thus some situations). Saying that needs a citation is like saying that "greasing your heels and walking on a waxed floor can cause slippage" needs a citation. If you think lessened maneuverability constitutes equal footing for all driving situations, you're the one that needs a citation.

Genocidealive (talk) 16:22, 12 June 2008 (UTC)
 * Please see WP:V. DigitalC (talk) 06:31, 8 July 2008 (UTC)


 * Please see WP:GetAGrip or WP:UseSomeCommonSenseForOnce. WP:V has very little to say about either. Greg Locock (talk) 10:59, 8 July 2008 (UTC)
 * And perhaps you should see WP:CIVIL. Per WP:V, "Editors should provide a reliable source for quotations and for any material that is challenged or is likely to be challenged, or the material may be removed.". The person that put the Citation Needed tag on was clearly challenging the issue. DigitalC (talk) 00:47, 10 July 2008 (UTC)

Everything in the article needs to be referenced, whether you consider it "common sense" or not. That is Wikipedia policy, period. It's also the best way to avoid edit-wars. Mikiemike (talk) 22:57, 11 July 2008 (UTC)

Costs of fuel economy-maximizing behaviors
Would it make sense for this article to also address the actual costs of fuel saving techniques? Starting an engine 25-50 times a day five days a week will cost you a new starter in a relatively short time. I would expect that to cost $300-$400 depending on the car. Engines wear the most during starting (no oil pressure) so one has to also figure in the costs of premature engine wear/failure and the high costs of the repairs. I believe the costs of saving fuel by many techniques will actually cost the vehicle owner more money, and actually expend more energy in the form of the energy to manufacture more replacement starters, engine components, and the fuel to ship them not to forget the petrol solvents used to manufacture and perform the repairs. All such actions also increase environmentally damaging byproduct. 98.193.70.212 (talk) 14:24, 11 May 2008 (UTC)
 * You need to find non-biased, third-party references to support your statements before they can be added to the article. SpikeJones (talk) 17:48, 11 May 2008 (UTC)


 * You make a point, 98.193.70.212; however, also consider that there are (hybrid) cars that automatically stop and start the engine, and presumably their starters don't wear out prematurely. So not all starters are the same.


 * Of course, for sake of the article, SpikeJones is right; everything must be sourced, no matter what. Mikiemike (talk) 23:05, 11 July 2008 (UTC)

Requested move
I am requesting this page be renamed to "Hypermiling," the most common and simple term. Other similar behaviors described in this article are only derivatives of hypermiling. Sebwite (talk) 00:51, 8 July 2008 (UTC)


 * I see no great advantage in renaming this sensibly titled article in favour of a neologism of limited ubiquity. Greg Locock (talk) 10:53, 8 July 2008 (UTC)


 * This is not just a neologism. This is the actual term widely used in the media, and by those who teach the techniques. The title "Fuel economy-maximizing behaviors" makes it sound more like a how-to guide. Sebwite (talk) 14:48, 8 July 2008 (UTC)

The current title of the article seems obtuse. The term hypermiling seems to have bonafide credibility in the major media outlets, however difficult that may ever be to verify. 842U (talk) 15:30, 8 July 2008 (UTC)


 * If it matters, the term hypermiling is already redirected to his page. So other than the previous comment about this being titled as a how-to guide rather than as an explanation of a specific term, we probably don't need to move anything. On the other hand, Hypermile was listed by the NYTimes as one of its noticed [2007 buzzwords], which ought to count for something. SpikeJones (talk) 17:20, 8 July 2008 (UTC)


 * I am aware that "hypermiling" (and some variations with other suffixes) redirect here. But given that it is the widely-used term in sources that would be considered reliable, and this is easy to verify, that is an important reason for renaming. Sebwite (talk) 17:29, 8 July 2008 (UTC)


 * Hypermiling is a subset of fuel economy maximising behaviours. Hypermiling is a wp:neologism. I agree the article could be retitled, but not to this buzzword. Greg Locock (talk) 00:16, 9 July 2008 (UTC)


 * Hypermiling and similar do appear in dictionaries, for example . Sebwite (talk) 01:23, 9 July 2008 (UTC)


 * Fair enough, although I'm not convinced that definition is useful "any vehicle driver seeking to optimize fuel economy by modifying their driving habits". So if I switch my engine off while I get the paper I'm a hypermiler? Do you agree that hypermiling is a subset of FEMB, and calling the whole article by the name of one of its subsections is wrong? Should we rename Skeleton to Femur? Possibly the simplest solution would be to create a new article Hypermiling and then move all the tosh into that.Greg Locock (talk) 02:39, 9 July 2008 (UTC)
 * Per that definition, no, switching your engine off while you get the paper is not hypermiling, as it is not a driving habit. (You can't be driving if you are outside the car). DigitalC (talk) 00:40, 10 July 2008 (UTC)
 * I actually thought about that, but I found that about 90% of the article refers to hypermiling, and the other 10% refers to derivatives thereof. Sebwite (talk) 19:15, 9 July 2008 (UTC)


 * Well, then your solution to this is to segment out those items relating to hypermiling from the other suggestions. Thereby meeting both goals of clarifying the hypermiling information as well as including other fuel-economy maximizing behaviours that are not hypermiling-related. SpikeJones (talk) 19:33, 9 July 2008 (UTC)


 * Anyway, one of my prime concerns is the HOWTO issue. Obviously, hypermiling is a notable topic with the amount of coverage it has these days. But listing a group of techniques along with a title like these does not seem to comply with WP:NOTDIR and WP:NOTGUIDE. This list of techniques does not link to other Wikipedia articles, rather the title link to the list. Sebwite (talk) 19:58, 9 July 2008 (UTC)
 * Start a new thread, topic-changer. It would be impossible to fully explain what hypermiling is without describing how it's done. You may not like that people engage in hypermiling behavior, but that doesn't mean that this encyclopedic article is a "guide".  I believe it does comply with WP:NOTGUIDE.Mikiemike (talk) 23:18, 11 July 2008 (UTC)

I went ahead and made the split. Sebwite (talk) 14:58, 18 July 2008 (UTC)

Was there a consensus for a split?
There seemed to be more opposition to the split than consensus for it, so I'm a little taken aback that the split was made.

If there is a split, I would think there would be two reasonable ways to divide up the information:

Division 1: Hypermiling is about the cultural phenomenon--names used in different cultures, origin of the term, popularity, media attention, contests and their outcomes, etc., where as ...behaviors would be about the actual techniques used.

Division 2: The Hypermiling article is about the extreme techniques that are used by extreme hypermilers, and the ...behaviors article is more ordinary advice like you might get from EPA, cartalk or AAA, though hopefully better validated than some of those things.

The present split seems to be roughly what I called division 1, but in reverse. That doesn't make any sense to me. I'd go ahead and implement division 1 or division 2, but I'd like to hear others opinions first...including whether we should revert. Ccrrccrr (talk) 01:17, 19 July 2008 (UTC)


 * Frankly it looks more like a tantrum than a reasoned attempt to split the article. As you say the individual techniques belong in this article, the cultural phenomenen belongs in Hypermiling, either as a subsection here, or possible in its own article. As an example, putting hybrid cars into hypermiling is ridiculous, since there are regular complaints that they do not achieve EPA MPG. At the same time I do agree that the title of this article is clumsy at best, if accurate. I don't know how to resolve the HOWTO problem, but I think that is a separate issue. Greg Locock (talk) 01:40, 19 July 2008 (UTC)
 * The split was wholly unwarranted and reverted. The excessive focus on the western marketing term "hypermiling" in this discussion ignores the reason this article was initially created. The content of Nepomania, etc, etc all shared essentially the same information. Stripping it out of here and discussing it as though it were solely or primarily related to "hypermiling" is disingenuous in the extreme and makes the entire work look even more unprofessional than it currently does. Notice that the splitter also removed the WP:OR template without explanation or cause. Let's focus on cleaning up what we have, not chopping it up and hiding it elsewhere, stripped of cleanup tags. MrZaius  talk  04:12, 19 July 2008 (UTC)

Bot report : Found duplicate references !
In the last revision I edited, I found duplicate named references, i.e. references sharing the same name, but not having the same content. Please check them, as I am not able to fix them automatically :) DumZiBoT (talk) 00:00, 13 August 2008 (UTC)
 * "impala" :
 * A graph of fuel consumption vs. speed for a Chevy Impala
 * www.nhtsa.dot.gov/people/injury/enforce/Speed Forum Presentations/ppt/White 1.ppt Graph of fuel consumption vs speed

Advanced Techniques/Reliable Source
http://metrompg.com/posts/xfi-pulse-and-glide.htm does not meet WP:RS - it is a blog, so in my opinion the pulse and glide section is effectively unsourced, and has been for two months, and should therefore be deleted. The DFAS section is incoherent gibberish that describes Drafting, so I propose that we delete that part and  the drafting section just picks up the DFAS acronym as an explanation. Autostop still reads like a how to section and needs severe editing. Greg Locock (talk) 22:38, 13 September 2008 (UTC)


 * Pulse and glide is quite a delicate topic. First of all, someone suggests to turn off the engine during the glide, and this is crazy: you lose ABS and steering aid. In addition, it makes no sense to everyone having ever studied physics: the air drag and many other frictions increase more than the speed of the car, so, for a given average speed, driving faster and slower makes you consume more fuel in the faster part than you save in the slower part. This P&G was born and works only thanks to... inaccurate readings of the car computers. I repeat, a basic knowledge of physics is enough to understand the crazyness of such approach. And this, as I wrote in the -now censored- P&G paragraph, is without taking into account the acceleration part (the pulse), where the car burns even more fuel than needed to run at constant speed. Are sources needed to write in an encyclopedia that 2+2=4? so for this. At least don't censor the paragraph completely, but leave an hint that the topic is discussed and not clear. I mean, leave it for the sake of Wikipedia reputation, nothing else. It can probably proved mathematically, but people believing in P&G would also be the people unable to follow the demonstration or (as it happened in my experience) the people taking into more account their "real experience" (…) than maths. —Preceding unsigned comment added by 84.163.124.237 (talk) 09:04, 14 September 2008 (UTC)


 * I don't see what is delicate about it. It actually works quite well in the right circumstances, the maths is obvious to even the average engineering student, once they understand BSFC maps. However I've never seen a reliable source that discusses it, so I will delete it. The whole thing. Completely. No hints. We don't do hints. Greg Locock (talk) 09:27, 14 September 2008 (UTC)


 * Dear 84.163.124.237, wiki policy says "no original research", so you have to cite references for your material. You are correct about the drag efficiency, but you are assuming that the engine has no idling loss and is equally efficient at all rpms and torques, which is not true (as Greg says).  See: Brake specific fuel consumption.  You're also assuming that the road is a constant slope, which it is obviously not.  If you turn the engine off and coast down a hill, that is technically a fuel-economy-maximizing-behavior, because there are no idling or accessory losses.


 * By the way, Greg Locock, the part of the website http://metrompg.com/ that is referenced by the article is not a blog; at worst there are selected blog excerpts (expert written summaries, etc), which is different than just some random blog. Yes, it's unfortunate that another part of the website is a blog, and it's confusing and misleading that the blog is linked-to in the sidebar, however you might want to take a second look at the material that is actually being referenced, because it does appear to be expert-level.  Considering the shortage of expert-level sources on this topic, I think some concessions are in order.  The essence and purpose of the WP rule's meaning is more important than its literal interpretation.  There are bound to be legitimate and reasonable exceptions now and then.  As I recall, WP even says somewhere that it is a strongly recommended guideline, but not a hard-and-fast rule in all cases.  Anyway, I challenge you to find better sources.  I've looked, and if your research goes anything like mine did, I think you may find it's not so easy to find perfect references on this topic.  Anyway, I've done quite a bit of editing work and continuing maintenance to keep everything sourced as much as possible.  So even if the sources aren't perfect yet, at least it's a lot better in this department than it was some months ago.  At least you can't complain that it's not sourced at all, so that's progress in my book.

--Mikiemike (talk) 01:11, 15 September 2008 (UTC)


 * If you could find the date of the Road and Track magazine that has been scanned into that website I think that would be a fine source. Greg Locock (talk) 02:57, 15 September 2008 (UTC)

Outlet for disputed content
There seems to be a lot of energy to put content here that doesn't really belong in an encylopedia. A good place for that could be the new Green Wiki,. There are fewer restrictions there, and this article could link to there. Ccrrccrr (talk) 00:49, 30 September 2008 (UTC)

Link not working
A link to a BSFC graph in the informative section on gear selection in a manual transmission vehicle is now not working. Not being very technically oriented, I'm not sure if a replacement graph I might insert would illustrate fully what the editor who inserted this section intended. I'll search the linked website to see if the page was moved, and any editor confident he or she has an suitable replacement may insert. NoHenry (talk) 19:18, 5 January 2009 (UTC)

~That's a shame, the new graph i found isn't as good. next time could you just flag it once on the article or on the talk page? Greglocock (talk) 22:38, 5 January 2009 (UTC)


 * I tried to find it on the original site, but couldn't. Here's the original link .  Maybe we should write to the webmaster and ask about it.  The new plot is very clear, but it would be better to have a regular spark ignition engine without a turbo to be more typical.Ccrrccrr (talk) 00:39, 6 January 2009 (UTC)

Advanced techniques: Coasting in gear
I'm surprised that coasting in gear is not mentioned in this article, while advises as coasting out gear and even coasting with the engine turned off (which has obvious repercussions on driving safety). Certainly since many vehicles feature a fuel cut-off when coasting in gear, such as described in this link: http://www.ecomiling.com/lessons/lesson5.html There is no doubt that coasting out of gear is unsafe and - unless the engine is turned off (which is even unsafer) - uses more fuel than coasting in gear. This should be added to this page, since it covers safe hypermiling practices. Wooter79 (talk) 00:52, 1 January 2009 (UTC)
 * Fixed it myself in the article Wooter79 (talk) 01:04, 1 January 2009 (UTC)


 * Does http://www.ecomiling.com/ qualify as a reliable source? There is no information about who wrote these "lessons".  How do we know this is not just another blog?  Show me a driving manual where it says that you must accelerate with little or no warning and if you do not it will be dangerous.


 * Lots of people have strong opinions on what is safe and what is not, yet far fewer people have references. I do not accept your opinions as fact.  According to WP policy, you must come up with a good source for your information.  Mikiemike (talk) 02:32, 3 January 2009 (UTC)


 * The "lesson" tells drivers to coast all the way to a red light. I believe this is not the most efficient behavior.  Here's an example:  Suppose a vehicle is traveling at 10 m/s toward a red light that is 100 m away, and the driver knows that the light will turn green in 12 seconds (due to having local knowledge of the light's timing).  If the driver simply coasts all the way to the light, the vehicle will reach the light in 10 seconds, which is 2 seconds before the light turns green.  Therefore after coasting nearly all the way to the light, the driver would have to bring the vehicle to a complete stop, thus wasting all of the vehicle's kinetic energy.  I contend that this is not the most efficient driving behavior.


 * Instead, suppose the driver decelerates the vehicle at 1 m/s2 for just the first second, then the new speed will be 9 m/s. The average speed during this second is 9.5 m/s, so the vehicle will have traveled 9.5 m during this time.  The vehicle is now 90.5 m away from the light, going 9 m/s, with 9 11 seconds remaining until the light turns green.  If the driver coasts the rest of the way, then in 9 10 seconds the vehicle will have traveled 81 95 m.  Thus the vehicle will be 9.5 5 m away from the light when it turns green.  The result is that the driver will have saved 81% of the original kinetic energy in the vehicle.  Clearly this is much better than the total loss of all kinetic energy resulting from coasting all the way to the light, and having to stop short.


 * It is somewhat counter-intuitive that braking can save fuel, nevertheless I have just proven that there is at least one case where this is so.


 * This example also illustrates that this is a complex subject. So we should have a little humility and not rush into making bold claims, especially if the claims do not have credible sources to back them up.


 * The conviction with which we hold our opinions does not necessarily equate to the veracity of the claims. Mikiemike (talk) 02:32, 3 January 2009 (UTC)


 * Without offering judgement on your analysis, I would like to mention an error you made. If the light turns green in twelve seconds (paragraph 3), and the driver brakes for only one second (paragraph 4), there are eleven seconds, not nine (paragraph 4 again) before the light turns green.  You might want to rework the example.  NoHenry (talk) 19:34, 5 January 2009 (UTC)


 * NoHenry, it appears you are correct. My mistake.  I had changed the numbers at one point, and I hadn't propagated my changes all the way through the example.  Just now, I updated the numbers and added a strikethrough to the old numbers.  Thanks.  My conclusions are still the same.  I have observed this phenomenon in my own experience with driving.  Another example of when this knowledge is useful is when you are turning left.  You can see all the cars, their speeds, accelerations, and most importantly the gaps between the cars.  You must time your vehicle to arrive at the intersection when there is a gap in the traffic, so that you can turn left without having to stop.  Mikiemike (talk) 12:56, 9 January 2009 (UTC)

If you coast in gear you are effectively braking the car by driving the engine around faster than it needs to. I won't insult your massive grasp of technical details by asking you to suggest how much this will matter (or even, heaven forbid, go and do an experiment), but it will slow the car significantly more than if it were in neutral. If you leave the engine running then you'll just use the idle fuel flow rate, about 0.3 gallons per hour. So, if you are coasting neutral with the engine off at 20 mph you'll be getting 67 mpg, roughly. That is pretty good. Not as good as infinity, which is what you'd get with the engine switched off, but still pretty good. I think you'd have to have some sort of death wish to switch the engine off in normal driving. Greglocock (talk) 04:14, 3 January 2009 (UTC)


 * I tend to agree, but that doesn't matter. We all have our opinions on how safe or unsafe these actions are, but for the sake of the article we must have references.  An editor can not simply add to the article: "You'd have to have some sort of death wish to do _________ ".  But you could say: "Charles Bronson says you'd have to have some sort of death wish to do _________ ".  Do you see the difference?  Mikiemike (talk) 12:56, 9 January 2009 (UTC)

acceleration section
The details of how to handle light most effectively are interesting, but as far as I can tell it's all WP:OR. I personally would be OK with you all having a debate about it on the talk page and finding something reasonable to put in, even though that is still a violation of WP:OR, but working out the OR through an edit war is not OK. So I cut out a bunch of stuff. Please discuss here before adding it back. Ccrrccrr (talk) 05:13, 13 January 2009 (UTC)

It is actually incredibly complicated, I agree trying to resolve it here is a good move. The first question you need to ask is : what am I trying to achieve? When we try and do this stuff for real we assume that the driver wants to achieve a certain AVERAGE speed, or if you like, journey time. There is then a tradeoff between accelerating briskly, to a lower cruising speed, or accelerating gently, to a higher cruising speed. The same needs to be sorted out for braking or coasting.

If you then add in traffic lights and phasing and triggering then the whole thing gets too hard. Greglocock (talk) 07:24, 13 January 2009 (UTC)

It'll be difficult of find good information on best ways to treat traffic lights, if it even exists. But much could be determined with logic, though I doubt it would meet OR policy. Tom Vanderbilt's book Traffic is a good starting point. He looks at the Minnesota's (IIRC) experiments with "Late Merge" vs other merging policies for managing construction traffic. They find that when congestion begins "Late Merge" is optimal, though the throughput at the bottle neck is the same as for early merge policy. The difference is that early merge extends the length of the queue at the bottle potentially interfering with other traffic. Late merging is only beneficial when congestion begins to happen though, and that is difficult to define. Principles inferred could apply to other situation.

Comparing time and fuel in more than brief mention is probably roaming off topic, since the focus is fuel not efficiency in general (though it is related to economy, it's too complicated to tackle here).

The best way to compare the two, as far as I can tell, is looking at dollars. 2008 US Per capita gdp per hour is about $4.97. Rough estimate is that at about $3.65 and cruising at 65mph the cost of fuel equals cost of time. However, I have my doubts that GDP is a good measure of productivity. There is a lot of paper only value included in gdp and price inflation doesn't always spread evenly.

Aaron shem (talk) 06:48, 14 January 2009 (UTC)

BSFC Graph
What about this one? 

Same one somewhat enlarged. 

It's from the AutoSpeed article on BSFC in footnote sixteen.

The article says the graph comes from a 1999 report prepared for the Canadian government by Sierra Research of California, which makes me believe it's the same one appearing in the now broken link referenced above.

NoHenry (talk) 19:24, 13 January 2009 (UTC)


 * The advantage of the one that's in there for the purpose of the discussion is that it has constant-power curves plotted on it.Ccrrccrr (talk) 19:47, 13 January 2009 (UTC)


 * Also it bears only passing resemblance to a real bsfc map. Juilain Edgar is a journalist, not an authority on engines. I think we need to keep looking there are some great ones out there posted by TDImeister, but only in forums.Greglocock (talk) 22:40, 13 January 2009 (UTC)


 * Producing our own illustration might be ideal--we could then include it on the page rather than in a link. I'd suggest asking TDImeister to do it for us, but I'd prefer a SI engine not a TDI engine.Ccrrccrr (talk) 01:23, 14 January 2009 (UTC)


 * I'm happy to do that as I have all the tools for the surface fitting and so on, what I don't have is a WP:RS for figures to put in. I agree it would be much better to do an SI engine. So, have a look for a table of torque vs rpm vs sfc, or bmep vs rpm vs sfc. I'll keep looking. Greglocock (talk) 01:29, 14 January 2009 (UTC)


 * It would be fairly easy to take the data from figure 11 on p10 ofin http://web.mit.edu/deweck/www/PDF_archive/3%20Refereed%20Conference/3_42_AIAA-2004-4553.pdf

It would be good to get information for gasoline engines in there, the prominent repetition of low RPM of diesel will confuse people and lead to inefficient driving.Aaron shem (talk) 01:03, 15 January 2009 (UTC)

Congestion and speed
The paragraph on congestion, speed and efficiency is now clearer to me. I still think it is out of place. This article is not about public policy for maximizing fuel economy, but specifically about what driving style can do. I'm going to edit it a bit but leave it in pending other people's thoughts about whether it belongs. Specifically, I want to be careful about the use of the term "efficient" because that can mean efficient in terms of fuel use or efficient in terms of getting as many vehicles through as possible. Certainly there can be synergies where both get maximized together, but it should be clear which is being discussed when the term is used.Ccrrccrr (talk) 13:34, 14 January 2009 (UTC)


 * Check out the discussion around p. 213 of this report that was cited in support of 45 mph being the speed at which one gets maximum throughput.  They consider the case of not doing anything to improve traffic flow and conclude that the extreme congestion results in very low emissions.  I'm not sure we want to get into that in this article, but traffic congestion can be a way to reduce emissions.Ccrrccrr (talk) 13:47, 14 January 2009 (UTC)

The page is about fuel economy. I take that to mean efficiency, but there could be other interpretations.

Anyway, I take issue with the statement in the report about emissions, especially the part about minimizing them. They are talking about overall consumption of fuel as the mechanism for reduced emission, because the traffic deters people from driving. However, this mean more emissions per vehicle. It also means more fuel is used per unit of economic output generated (ie, more fuel per utility). Here, reduced emissions is a euphemism for "decreases output and efficiency".Aaron shem (talk) 00:46, 15 January 2009 (UTC)


 * I agree, the use of congestion to discourage people driving is not very relevant to an article about Fuel economy maximizing behaviours. Greglocock (talk) 01:19, 15 January 2009 (UTC)


 * Aaron, you take issue with the reference. If we can't rely on it, we ought not to for the rest of that paragraph and thus we should delete the whole paragraph.


 * Greg, am I interpreting your comment correctly that we ought to remove the whole paragraph? That was what I had done originally, but that deletion got reverted and I got complaints.Ccrrccrr (talk) 01:37, 15 January 2009 (UTC)

The statement is factually correct, but can be misleading to the lay person and is off topic.Aaron shem (talk) 02:06, 15 January 2009 (UTC)


 * So am I hearing a consensus for deleting the paragraph again?Ccrrccrr (talk) 03:21, 15 January 2009 (UTC)

Are you serious?Aaron shem (talk) 03:38, 15 January 2009 (UTC)


 * I was serious, so I guess I misunderstood your comment. Are you suggesting that some aspects are off topic and other are not?  Where do we draw the line?Ccrrccrr (talk) 02:09, 16 January 2009 (UTC)

Efficiency.Aaron shem (talk) 03:42, 16 January 2009 (UTC)

Tailgating
How is this relevant to this article?

Drafting: should be integrated in it's respective paragraph

Coasting in neutral safety: seems biased and unneeded.

quote: The general practice of coasting in neutral is against the law in many American states, yet there are exceptions to this law, and some places advocate its use in certain circumstances, for example: "If you are on ice and skidding in a straight line, step on the clutch or shift to neutral.

Hey I guess that means I can go shoot someone, because I can shoot someone in self defense, therefore... —Preceding unsigned comment added by 124.182.111.44 (talk) 08:35, 10 February 2009 (UTC)


 * This isn't a howto article. It's descriptive of what people do, not prescriptive. People do that, whether we think it's a good idea of not.  On the other hand, I agree that the commentary you quote, and a lot of this article, doesn't belong in an encyclopeda.Ccrrccrr (talk) 13:10, 10 February 2009 (UTC)


 * I agree. Let's decide on a structure for the whole article and then move relevant parts into that structure and zap the rest. Greglocock (talk) 22:53, 10 February 2009 (UTC)

Rewrite?
Above, Greglocock suggests a re-write/restructuring of the article. That's a lot of work, but, despite the wealth of good information here, it seems to be stuck in a mode that isn't really encyclopedic. One idea is to move the how-to and OR stuff somewhere other than WP. How about starting a hypermiling wiki page on wikia somewhere, like on green wikia [green.wikia.com]? We could start by copy and paste this whole article there. Then it could develop with more detail on specific topics, including more how-to and OR, while this page would get trimmed, with links there added for the stuff people want to say but that doesn't fit on Wikipedia?Ccrrccrr (talk) 12:38, 11 February 2009 (UTC)

Is this true?
Studies have shown speeds just above 45 MPH allow greatest throughput when roads are congested[17]

The "greatest throughput" doesn't it mean that the highest speed allows for the greatest throughput? Am I missing something? Can you get more cars at 45 mph then at 55 mph?

Also, I cant find the 45 mph paragrapg on p 213 anywhere.

3: This study refers to a specific highway, with a specific build, shape, bitumen, at a certain altitude. As is this reference would not apply to any highway, at any location. Even changes like the trucks to cars ratio would change this number, so I would really like to see the exact wording of the reference where this number is taken from.

124.182.111.44 (talk) 07:37, 10 February 2009 (UTC)


 * I don't know the specific numbers but it works the other way around--as you push more cars onto a road, it gets congested and the speed slows. The two factors fight each other--more cars means more throughput, but lower speed means less.  The net result is that the throughput goes up as you put more cars on until a critical point at which the traffic grinds to a halt.  So somewhere in between is the max throughput point, and this is saying that that's about 45 mph.


 * In fact I actually think this traffic engineering topic doesn't belong in this article.Ccrrccrr (talk) 13:07, 10 February 2009 (UTC)

It's true, but only for a specific road. And, it doesn't mean that a 55mph speed limit is less efficient than a 45 speed limit, as some might infer. What happens is, for that road, after safe capacity is reached for a speed cars slow down to make more room. After slowing to 45mph, the amount of extra room made no longer improves throughput.

Throughput will always be higher at higher speeds, unless they prevent additional vehicles from entering the traffic flow.Aaron shem (talk) 02:42, 8 April 2009 (UTC)


 * "Throughput will always be higher at higher speeds." I'm not sure what that means.  If you have few enough vehicles per hour (vph) that there is not problem with congestion slowing the flow, then the throughput will be determined by how many vehicles enter the road, not by the speed they travel.  So I'm not sure what the experiment is in which you have higher throughput at higher speeds.  Ccrrccrr (talk) 20:28, 9 April 2009 (UTC)

Lazy merge suggestion with hypermiling
Oppose FEMB applies to any vehicle, not just publicity hounds. People suggesting merges should start a section to justify their stupid ideas.Greglocock (talk) 12:18, 13 April 2009 (UTC)

Efficient Speeds section
Made the following changes to this section.


 * Changed a malformed link meant to direct to the EPA 2005 Fuel Economy Guide to what I think the author intended.


 * Changed the average optimal fuel efficiency speed back to 55mph from 60mph. The Guide was used as the basis for the increased figure, but I don't see this stated anywhere in it, and the graph on page five doesn't seem to support that claim.  In the 2009 version of the document, the graph which is on page six peaks at 50-55mph, with a slight but perceivable decline at 60mph.


 * Eliminated this link, which evidently is the basis of the edit summary claim that people have reported getting better mileage at 75 to 80 mph than at 55 mph.  Using message board posts for citation raises  reliable sources issues.  The poster's claim to have gotten 29 mpg at 75 mph while only 22 mpg at 55 mph likely also qualifies as an  extraordinary claim

Comments welcome

NoHenry (talk) 20:38, 12 January 2009 (UTC)


 * The text in the 2009 doc still uses the 60mph limit. I recognize the graph as a cut and paste of a previous study.  Don't know why they'd use it.  I'll look into it if I remember and have the energy this weekend.  Of course, if that's the case, that as makes the 2005 curve suspect too.


 * Certainly agree on the cite. Unfortunately, it is almost impossible to find fuel consumption plots for cruising speeds.  I'm amazed that people don't make them given that so many cars have computers on board.  However, it is not an extraordinary claim.  Given the average for 2005 optimal cruise speed was ~60 and many cars are as low as 35, many cars must get higher for a 55 or 60mph speed to be normal.


 * The text clearly indicates that the EPA sees the speed where fuel efficiency begins to decline as near 60mph, rather than 55. The curve is pretty flat between 45 and 60 in the graph in 2009, of course this is subjective. This graph looks very familiar, I'm pretty sure it's a cut-and-paste from another report.


 * I found a the data and calculation methodology on the EPA site, but don't when I'll get around to studying and analyzing it.


 * http://www.epa.gov/oms/fetrends.htm#report


 * Aaron shem (talk) 02:41, 14 January 2009 (UTC)


 * Disagree with worrying too much about a fine interpretation of that graph since it doesn't identify whether it is an average or whatever. The graph in the 2009 report actually peaks at 50 mph. Here is a graph which makes claims of better mpg at  75 mph or 80 instead of 50-60 rather dubious (ie totally laughable, but I'm being polite) http://www.greencarcongress.com/2006/05/fuel_consumptio.html Greglocock (talk) 05:08, 14 January 2009 (UTC)


 * That's interesting. Wish they linked the study, and that I knew german.  And they showed the other 8 cars, how and why they picked them.  And I knew their methodology.


 * I'm pretty sure the graph in the 2009 one based on the 1999 study of 9 cars, http://ntl.bts.gov/lib/5000/5800/5844/21st_edition/Edition21Chapter07.pdf


 * The peak for 1997 cars is clearly 55mph. The 2009 guide peak can at best be said to be between 50 and 55.


 * It's much more clearly defined in the bts 1999 study.


 * Aaron shem (talk) 07:33, 14 January 2009 (UTC)


 * Aaron Shem says:
 * "The text clearly indicates that the EPA sees the speed where fuel efficiency begins to decline as near 60mph, rather than 55. The curve is pretty flat between 45 and 60 in the graph in 2009..."


 * The text does not say where it begins to decline. It says "each 5 miles per hour (mph) you drive over 60 mph is like paying an additional 10¢/gallon."  That's a statement about the slope of the graph in the region above 60 mph.  I think the reason they say that is that the slope in the 55 to 60 mph range is small, and so they'd have to make a much more complicated statement about "the first 5 mph you drive over 55 mph is like paying an extra 3 cents per gallon; beyond that point each 5 mph is like paying an extra 10 cents per gallon."  That would be too complicated for the simple bullet point they were trying to create.  Since the text does not state where the optimum is or where it begins to decline, we have to go on the graph or on other sources.


 * I agree that the curve is pretty flat between 45 and 60. That means that the optimum is somewhere between 45 and 60.


 * As far as giving advice to drivers, if you believe that that curve is representative of a typical vehicle, it might be good advice to go no faster than 60 mph, rather than advising going 50 to 55 mph. As we can see, it doesn't make a big difference. But advising that 60 mph is the maximum efficient speed is different from advising that mpg is highest at 60 mph.  The latter might lead to the conclusion that's it's wasteful to drive at speeds below 60 mph.
 * Ccrrccrr (talk) 13:30, 14 January 2009 (UTC)


 * Aaron shem, the claim the message board poster made about getting better mileage at 75-80 mph is likely an extraordinary claim by itself, but he goes even further, saying the mileage rises from 22mpg to 29mpg.  I don't know how to figure out percent increase but even I can tell that's significant. NoHenry (talk) 17:31, 14 January 2009 (UTC)

I agree that it can't be determined one way or the other (55 or 60).

The CO2 comment doesn't belong in this section. Reducing CO2 is a motivation for improving fuel economy is a good thing to mention in the introduction of the page, but this is about fuel-economy, not CO2 economy. Getting into it further is off topic.Aaron shem (talk) 00:28, 15 January 2009 (UTC)


 * I assume that by "the CO2 comment" you mean the reference I added for 35 mph being optimum. The plot I saw in the report is in terms of CO2.  Minimum CO2/mile means maximum mpg/mile.  That's not there for the purpose of discussing CO2--it's only there because the plot happens to be in units of CO2 rather than units of mpg.  Because the link between the two is trivial, the CO2 plot is useful data.  Ccrrccrr (talk) 01:32, 15 January 2009 (UTC)

Sorry. Yes, I think that's it. I was skimming differences and didn't realize I was reading a description of the reference. Everything looks good.

And my apologies for misreading the 2005 EPA graph, can't believe I did that.Aaron shem (talk) 02:18, 15 January 2009 (UTC)


 * Great--that makes sense why that threw you on a first scan.Ccrrccrr (talk) 03:20, 15 January 2009 (UTC)

"The optimum speed varies with the type of vehicle, although it is usually reported to be 35 mph (56 km/h) or higher."

It is not "usually reported" that the optimal speed of a vehicle for fuel economy is 35 mph, just because that sentence has more citations. Almost anywhere you look, including government publications says 55 mph is the optimal speed."174.3.107.124 (talk) 19:57, 3 October 2009 (UTC) 174.3.107.124 (talk) 20:00, 3 October 2009 (UTC)


 * 55 is higher than 35, so 55 is included in "35 or higher". So the text is correct.  There might be other ways to phrase it--for example it might say "typically reported to be between 35 and 55 mph".  I'm not sure I remember how it ended up phrased the odd way it is now.--Ccrrccrr (talk) 22:25, 4 October 2009 (UTC)

Seems a little non-neutral about coasting in neutral
In particular, I don't like the idea that braking is the only viable alternative in any emergency and, therefore, drivers won't suddenly and unexpectedly need engine power. It's amazing how few people understand that a V8 is a safety feature. There is no need to make that misconception even worse. -.-

I'd have just deleted that line, but it's kinda the basis for the whole section, so... Cite or rearrange or something?

J.M. Archer (talk) 20:27, 1 March 2010 (UTC)

Coasting in neutral.
In the article it says that coasting in neutral is illegal in many jurisdictions. I've heard it in several places, and even in my drivers handbook. But I just have one question. How is a police officer going to tell if your coasting in neutral, versus coasting in gear? Vandalism destroyer (talk) 08:44, 14 August 2008 (UTC)


 * It isn't that hard. If the traffic condition changes and you don't go immediately--and particularly if you start roughly--it becomes pretty obvious that you weren't in gear when the change happened.


 * In practice, I completely ignore this rule as the alternative often involves revving my engine in order to downshift, which will most assuredly attract unwanted police attention. But I'm more a "do as I say, not as I do," kind of guy anyway.


 * J.M. Archer (talk) 22:30, 1 March 2010 (UTC)

Additional thoughts.
Not changing anything but hopefully helping some of you that appear to have questions?

I am not sure how the exact format occurs in Wiki but it’s the content I am concerned with.

Hypermiling is simply beating the EPA of your vehicle.

Legality of being in N. In most jurisdictions in the US, it is being in N while going downhill, not being in N that is illegal.

FAS or Forced Auto Stop is not a hybrid specific technique as they do this automatically, it is a non-hybrid technique.

Control in a FAS. Since some above have no experience with it, they may not understand you do have all your safety equipment included with the car including your Air bags, ABS, TC, EBD, BA, VSC and whatever else you can think of. Full power brakes are good for a few solid pumps as well and if you needed to use them for more than that, you came into the condition to fast anyway and should have been using fuel cut with engine braking. Power steering? Every single journalist I have had a clinic with in a non-hybrid gets to experience a FAS and they all find out they can steer with one finger at speeds above 15 mph.

Cost savings of hypermiling? 48.5 mpgUS vs. 24 mpgUS for the average Accord driver over 105,000 miles. With an average fuel cost of $3.00 per gallon, that is $6,500 + USD. Tires at max sidewall last longer as well. Still the OEM pair on the Accord vs. most Accord drivers installing a new $600 set at 60,000 miles. M&R, (1) new starter after ~ 24,000 starts to the tune of $500. Nobody FAS’ as much as I used to in the Auto tranny Accord. With the manual transmission equipped vehicles, they can go for basically ever. Basjoos ahs over 240,0000 miles on his Stick and has been bump starting possibly as high as 50 times a day for the entire time he has owned the vehicle while on the original clutch. Brake jobs? A thing of the past as they are used so rarely.

Safety. Speed was killing upwards of 46 individuals with thousands of injuries per day in the US. Hypermiler’s don’t speed but they do follow the speed limits.

Speed differentials… 15 mph on the Interstate is actually a lower differential than what most people in their vehicles are driving around in parking lots with people dashing between parked cars and such. I have yet to hear of an accident because of a hypermiler following the speed limits and a speeder not following the speed limits because the differentials are so low but it “could” happen.

Good Luck

Wayne Gerdes


 * Not accurate, Wayne. State laws generally prohibit coasting downhill (per my own research; take that for what it's worth). However, state and local laws regarding coasting are only part of the picture. Texas rules, for instance, seem to indicate that the vehicle should in gear any time you're traveling at more than 10MPH, which would preclude most any other form of coasting. Whether or not this bit of advice rises to the level of a statutory prohibition on coasting is not apparent from the handbook the DPS hands out.


 * It should also be noted that statutes often require that vehicles remain in gear at intersections/stoplights/etc.--though I figure that probably plays into the whole hyperthingy quite well if you're going to turn it off at the intersection anyway. >.>


 * J.M. Archer (talk) 22:36, 1 March 2010 (UTC)

"Choice of gear" section
The section on "Choice of gear" is unclear. Currently it reads: "Engine efficiency varies with speed and torque, as can be seen in a plot of brake specific fuel consumption.[20] The optimum efficiency point is around 1750 rpm and 90% of full throttle for this turbo-diesel engine." First of all, the reference given for the first sentence is a broken link. Not only that, but it seems like it was not actually a reference supporting the statement, but rather an example plot. Secondly, I cannot figure out what turbo-diesel engine that "this" engine is supposed to be referring to. Thirdly, diesel engines do not have a throttle, thus they cannot have "90% of full throttle." I do not know enough about this topic to suggest specific corrections. --66.18.238.243 (talk) 04:09, 11 November 2010 (UTC)

Skid School Citation and Brake then swerve section
The page/site linked to doesn't have any information on what the citation referred to. The info (that braking allows for faster swerving) is incorrect and dangerous. Braking is more likely to turn a swerve into a skid http://www.wikihow.com/Drive-Tactically-%28Technical-Driving%29 I deleted the section. 192.91.147.35 (talk) 22:01, 22 February 2011 (UTC)

Is this either too obvious, or too facetious?
I've mulled over this for a while, because it occurs to me that the absolute best way to maximise fuel use is to not use it at all - by using alternative methods such as car sharing, walking, bicycles, etc.

I know that's not strictly what is meant by the term "Fuel economy-maximizing behaviors", but it is a viable option, and one that many people use to save fuel. Is it worth creating a small section to comment on this?

I thought I'd bring it up on talk first, in case people thought I was being facetious or sarcastic. a_man_alone (talk) 09:42, 23 September 2011 (UTC)

Auto-stop ... Poorly written ... Removed, etc.
Sept 25, 2012: I just eliminated this section by removing the "forced stop" stuff and renaming the section "Coasting in neutral". I then transferred the paragraph on drafting to the section on "drafting". There's still of lot of cleanup needed for the content which I didn't do. Also "Coasting" may not blong in the "Advanced" main section. David Lawyer

The section "Auto-stop, forced stop, and draft-assisted forced stop" is a jumble of information and lacks organization. The terms are not clearly defined. Someone who has a mastery of these terms (and can write well) should rework this section. —Preceding unsigned comment added by Ken444444 (talk • contribs) 01:06, 27 June 2008 (UTC)
 * Well, in my (David S. Lawyer) opinion much of it should just be deleted and the confusing terms not defined. I've noticed them used on hypermileage sites but forced stop has come to mean just coasting in neutral where often you don't stop at all.  It can be part of pulse and glide and thus the word "stop" shouldn't be used.   Originally forced stop meant coasting to a stop in neutral.  Coasting is already covered under "basic techniques" but it's inadequate.  But some useful info in this section could be put elsewhere prior to deleting the section.

Here's a quote from it: "Draft-assisted forced stop, a variation of the forced (auto)stop (sometimes abbreviated as D-FAS), involves turning off the engine and gliding in neutral while drafting a larger vehicle, in order to take advantage of the reduced wind resistance in its immediate wake" First, the words "forced stop" is obfuscation. At first I reasoned that the car behind the truck will have both aerodynamic drag (less than if the truck wasn't in front of it) and rolling resistance and will be slowing if the car is in neutral. Thus I claimed that it would soon fall back and recede from the wake of the truck. But checking the internet shows I was likely wrong, at least for some cases.

It seems that aerodynamic drag can be reduced to almost zero and may in some cases go negative. One person on a bicycle reports not only coasting behind a vehicle, but having to brake as well. Others report being able to coast most of the time. If these are true, then aerodynamic drag has in effect gone negative, or in other words there are aerodynamic forces pushing the following vehicle forward enough to overcome its rolling resistance.

One could try very short interval pulse and glide here when it's not possible to coast all the time.

If no one soon objects, I hope to eliminate this section, revising other sections to cover whatever relevant and significant content this section contains.

66.81.198.157 (talk) 08:25, 22 February 2012 (UTC)

Acceleration
"Fuel efficiency during acceleration generally improves as RPM increase until peak torque"

It's absolutely unclear as to what the above means. —Preceding unsigned comment added by 67.87.220.121 (talk) 13:33, 21 August 2010 (UTC)


 * You're kidding, right? It means that fuel economy improves as you accelerate, until the revs reach the maximum torque generated by the engine - after that economy starts to drop off again.
 * Of course, whether it's true or not, I couldn't say - but it's plain English.  a_man_alone (talk) 17:33, 21 August 2010 (UTC)


 * He wasn't kidding. If a car has the driveline connected, then the revs stay fixed if the speed stays fixed.  To get more torque, just push down on the accelerator pedal and the revs stay about the same for an instant.  RPM and torque are independent variables that one may select but RPM's may only be selected at discrete values.  The gas pedal depression selects torque and the gear you're in selects RPM (as does vehicle speed also).  Obviously the driver has less control over the RPM variable.  But on a dynamometer test stand, one can fully control the RPM's by varying the load.

If you look at a BSFC map you'll see that one may obtain fairly high torque at all RPM's. At high RPMs and high torque fuel efficiency drop. Look at the map at Brake Specific Fuel Consumption.

OK, I plan to edit this. — Preceding unsigned comment added by 66.81.29.34 (talk) 07:30, 23 February 2012 (UTC)

Link to David S. Lawyer's article removed
I'm the above person and author of a self-published article on my webpage entitled "The Case for Coasting: Energy-efficient Driving" See Case for Coasting. I added a link to it but someone removed it claiming that my self-published article doesn't constitute a reliable source. But I'm agreeing with its removal for other reasons.

My original argument for retaining it was that I'm sort of an expert in this field and my Senior project at UCLA in 1957 was on automobile fuel economy and specifically on carburetor testing. Using an engine test stand I found experimental points on the BSFC map. A published journal article (published by the Rand Corporation, et. al.) somewhat related to this topic was "Optimal Train Velocity and Size" which may be found on the Internet. Thus I think that I may meet the Wikipedia criteria for use of self-published material on this topic. After looking up articles on Pulse and Glide on the Internet, I've found some new significant references, one of which is a PhD thesis on the topic that isn't as good as it should have been. So I'll add these to the wiki article and possibly to my own article. My article was rather hastily written, doesn't cite enough references and much of it is like a howto. I may work on improving it but I haven't yet had time to do so, so I agree with its removal. Perhaps the revised version (if I do it) will be acceptable for WP to cite. 66.81.122.237 (talk) 07:18, 24 March 2012 (UTC) — Preceding unsigned comment added by 66.81.199.254 (talk) 07:22, 20 February 2012 (UTC)

U.S. View?
I removed the tag at the start of the article that claimed that the article only represented a U.S. view. Well, it's true that it does represent the U.S. view but if there are different non-US views, I didn't find them on the Internet by searching in English. The auto technology is about the same worldwide. I'll now search the Inet in Russian on this topic. David Lawyer.66.81.120.118 (talk) 21:18, 27 September 2012 (UTC)

While modern hybrids come with built-in trip computers which display real-time MPG [...] most gasoline powered vehicles do not have this as a standard option (although some luxury cars do).

Is this true in general, or only in U.S. I think that most cars sold in Europe have a built-in trip computer. --Jirka6 12:33, 18 October 2007 (UTC)


 * I have a 2007 Chevy Impala LS (V6 Engine) that has a built-in trip computer, and displayes real-time MPG. I know Impala is not a luxry car or a hybrid, so that quote is inaccurate.12.152.160.239 (talk) 18:36, 3 June 2008 (UTC)

Drafting
The current drafting section states nothing other than drafting is dangerous & quotes mythbusters. I wonder what extensive superfluous tests they performed to find this answer. While drafting, the distance to the vehicle in front of you is much smaller than the National Safety Council recommended 3 seconds. The closer you are to the vehicle in front of you & the larger the vehicle, the greater the effect on fuel savings. --User:funkasaurus 14:52, 10 Dec, 2009 (EST)