Wikipedia:Articles for deletion/Car speed and energy consumption


 * The following discussion is an archived debate of the proposed deletion of the article below. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review).  No further edits should be made to this page.

The result was merge‎__EXPECTED_UNCONNECTED_PAGE__ to Energy-efficient driving. As it seems from the discussion here that such a merge has already taken place, the history must remain for fulfillment of attribution requirements regardless of the redirect's utility. Seraphimblade Talk to me 09:08, 5 December 2023 (UTC)

Car speed and energy consumption

 * – ( View AfD View log | edits since nomination)

Essay. The article is a high school level analysis of air drag, with plenty of OR, and is factually incorrect to boot. See also this discussion. Fermiboson (talk) 12:59, 18 November 2023 (UTC)
 * Note: This discussion has been included in the deletion sorting lists for the following topics: Science, Engineering,  and Technology. Fermiboson (talk) 12:59, 18 November 2023 (UTC)
 * the presented analysis actually is slightly above secondary education level in the Netherlands, so above high school level in the US: there rather on the level of first year university physics. The analysis is meant to be accessible to advanced high school students, within the scope of the Wikipedia mission.
 * "plenty of OR", probably meaning "plenty of Original Research", is factually incorrect, as the complete argument in the article was condensed from the referenced book/website of MacKay, Science Advisor to the UK Department of Energy 2009-2014.
 * submitter of this deletion proposal wrote on 19 November on her/his talk page "in short, I’m not disputing the factuality of the derivations in the article, but WP:NOTTEXTBOOK applies.", so she/he apparently retracted the complaint of "incorrectness to boot". I am correcting the textbook style i hope satisfactorily for all, by comparing the article with, e.g., Drag (physics). Thank you, Hansmuller (talk) 09:19, 27 November 2023 (UTC)
 * Delete - per nom. Sgubaldo (talk) 13:24, 18 November 2023 (UTC)
 * Merge with Fuel economy in automobiles. While the analysis presented in this article leaves much to be desired, the topic itself is notable enough to be included as a section in the proposed target. Owen&times; &#9742;  22:14, 18 November 2023 (UTC)
 * Delete I don't see the merit in merging content that has to be fixed wholesale before merging, rather than writing from scratch whatever we don't already have in the suggested target article. XOR&#39;easter (talk) 00:29, 19 November 2023 (UTC)
 * Keep @Fermiboson @Ldm1954 The physics is incorrect? No, everybody, also the referenced nice papers by Kenneth Holmberg et al. (2012, 2013), agrees we have 1. acceleration, 2. air drag, and 3. further friction, and the applicable formulae. The quoted "5% air drag" holds only at constant 60 km/h, while the wikipedia article considered the quadratic effect over a range of low and high speeds. It is irrelevant for the thrust of the article: there is basically a quadratic dependence on speed of energy consumption, everybody agrees on that. The source of the Wikipedia article is the report by professor MacKay, official scientific adviser to the British government, the book Sustainable energy without the hot air 2008, free online www.withoutthehotair.com. We can easily incorporate the results of Holmberg et al. in this Wikipedia article. Merging? the article with other long articles muddles the arguments both ways, the TooLongDidNotRead effect.
 * Wikipedia needs a relatively simple article on the vital subject of energy consumption by cars and the effect of speed, right? Thank you, Hansmuller (talk) 13:04, 19 November 2023 (UTC)
 * Wikipedia should have an article, but only if it is correct. The current Wikipedia page states:
 * "At higher speed the energy consumption of a car per unit distance increases proportional to the square of the speed. This is caused by the air drag which dominates over the tyre rolling resistance at high speeds."
 * This is misleading as it is focusing on the 5% contributions, and ignoring the dominant 95% internal loses due to friction in the engine/transmission and also the efficiency of the engine etc as a function of speed.
 * Delete, and perhaps @Hansmuller will write an accurate version that includes all terms Ldm1954 (talk) 13:40, 19 November 2023 (UTC)
 * Thanks for the suggestion which i followed up. The dominant contribution of heat losses at low to moderate speeds has been included in the article. At high speeds however, air drag losses exceed other losses, refer to Graph 3 and the discussion in the article. Thank you, Hansmuller (talk) 10:08, 27 November 2023 (UTC)


 *  Keep Merge Delete I've edited Energy-efficient driving to include those parts of the subject article I consider notable.
 * The case presented against this article is weak.
 * The case claims is is "high-school level analysis"; the audience of Wikipedia includes high-school level readers.
 * The case claims WP:OR citing no examples.
 * The case claims the article is factually incorrect citing a discussion which includes exactly one -- disputed -- claim of incorrect content.
 * In the linked discussion the "tone" of the article was disliked. It seems to me to be a completely typical Wikipedia article.
 * The case did not make the claim that the topic was not notable or otherwise unsuitable for Wikipedia.
 * It is possible that only a minimal case was presented because it was assumed that everyone will vote delete.
 * The major issues I see with the article are
 * Title seems a bit non-encyclopedic.
 * Relies primarily on a single source
 * Contains disputed claims.
 * These are all issues that can be repaired. Johnjbarton (talk) 16:16, 19 November 2023 (UTC)
 * @Johnjbarton and also @Hansmuller, please look at Fuel economy in automobiles. This has a comprehensive list of the energy consumption contributions, which is far larger than the two in Car speed and energy consumption. You can also look at the similar information in Speed and fuel economy studies, and the comparable article in Energy-efficient driving plus there are numerous Google searchable articles from organizations such as AAA, RAC, DOE as well as popular science articles. The energy consumption is a very well-trodden topic, being a balance between $$$ for simple steels compared to superalloys or refractory metals versus engine efficiency, drive train and related frictional losses and other contributions such as drag and rolling friction. Ldm1954 (talk) 21:41, 19 November 2023 (UTC)
 * Comment As I said on the physics talk page, comparing this article to Fuel economy in automobiles is off base. I think the thrust of the article is actions existing drivers can take. Merging this content into Energy-efficient driving on the other hand, would be a win. That article is more comprehensive and yet it has no reference to Mackay or to Holmberg et al The vehicle speed section is weak compared with this article. Johnjbarton (talk) 23:39, 20 November 2023 (UTC)
 * I'm working at it, thanks.Hansmuller (talk) 22:16, 23 November 2023 (UTC)

Note: the physics is sound, according to the MacKay source and further literature. The referenced Holmberg/Erdemir articles, incorrectly used for refutation, actually support the Wikipedia article: 1. Holmberg et al. / Global energy consumption due to friction in passenger cars / Tribology International 47 (2012) 221–231 agree with this Wikipedia article, they state on page 223:

"The external air drag is the air resistance of the car when it moves on the road. It is proportional to the square of the driving speed and directly related to the size and shape of the vehicle, usually expressed as a multiplication of the drag coefficient by the projected front area [34,35]. In this study, 60 km/h is assumed as an average driving speed for all cars globally in urban, highway, and any other kind of driving.". Holmberg et al. do not further address the effect of speed.

2. Holmberg et al., Global energy consumption due to friction in passenger cars, transportation and industry, STLE Annual Meeting, Detroit, USA, 5-9.5.2013, echo the MacKay argument for a quadratic dependence on speed on their pages 8 and 9, with graphs similar to MacKay we can use as reference in the article, and refine the argument on other sources of friction.

Air drag losses dominate at high speeds, Holmberg/Erdemir agree.

Thanks for considering this matter, important for traffic air pollution vs. car speed as well, Hansmuller (talk) 13:35, 19 November 2023 (UTC) Please add new comments below this notice. Thanks, CycloneYoris talk! 07:33, 26 November 2023 (UTC)
 * Merge with Energy efficiency in transport. Exact same topic with duplicate material. better covered in other page बिनोद थारू (talk) 05:44, 26 November 2023 (UTC)
 * Energy efficiency in transport is about different modes of transport, not about the effect of driver actions on energy efficiency. Energy-efficient driving is a much closer match. Johnjbarton (talk) 15:31, 26 November 2023 (UTC)
 * agree बिनोद थारू (talk) 18:09, 26 November 2023 (UTC)
 *  Relisted to generate a more thorough discussion and clearer consensus.
 * Apologies to Hansmuller for going so long without replying. I will respond to his points both on my tp and here below.
 * In summary, my argument is not just that the article currently is an essay, although it undoubtedly is (I can elaborate more on this if need be but don't see the need right now), but that it can be nothing but an essay, under the area that the title delineates.
 * With regard to the factual accuracy claim, I based it entirely upon Ldm1954's looking into the source paper, for which I would also like to apologise as I should have done more extensive research myself. That said, while maybe "factually inaccurate" is not the most precise term, I do think that the article cannot be written in a manner where due weight is given. Since car speed is such a minor portion of the efficiency of automobiles (this part I think everyone here agrees with), any article that talks about only the impact of car speed is going to create an impression of disproportionate impact. In any case, that is not my main point, and if you still want me to remove "factually inaccurate" I am open to doing so.
 * The article currently cites two papers. One of these papers talks about a factor of energy consumption independent of speed, and the other is essentially an appendix to a popular policy document (which to be fully honest looks self-published to me, but I don't see anything wrong with the content so let's roll with it.) Everything else is a textbook, relating to the elementary derivation of the v^2 formula for air resistance (and other forms of resistance). We can cut all of that and simply cite the proportionality to the papers involved since there is no need to piece together our own derivation when the result is accepted. (Notable pieces of OR that would be cut include, for example, "energy consumption over a distance" section.) We are then essentially left with:
 * A reproduction of the proportions of modes of energy loss from said paper;
 * A reproduction of a graph of energy loss vs velocity from two papers;
 * A description of the trend represented in such graphs.
 * Note moreover that:
 * A dependence of efficiency on speed is not the major focus of the one paper that actually mentions it.
 * The experimental results from aforementioned paper have nothing to do with the v^2 dependence.
 * With this in mind, what can the article actually say? "Theoretically, energy consumption scales as v^2. Because of 'various factors', this doesn't actually happen at all (see graph). Also, it turns out other things have far more impact on energy consumption than car speed does, so it doesn't actually matter that much unless you're on a highway." If we have to mention all kinds of different factors not included in the title to have an article, then essentially throw our hands up and say "see results here, which we can't predict, but doesn't matter anyways", why not simply do all that at the place where this is already done? Fermiboson (talk) 04:12, 28 November 2023 (UTC)
 * Some additional notes, as the above message was getting clunkier and clunkier with every note I tried to add and edit into it:
 * There are still claims I consider factually inaccurate in the article. For example:
 * The graph captions and text don't really mention the fact that there is a large mismatch between v^2 predictions and actual data. I personally had to read through the thing three times, and the associated source twice, before I figured out what was going on.
 * That air pollution is proportional to the speed squared. Neglecting how ill defined "air pollution" is (total emitted pollutants? Pollutant concentration?), the statement "air pollution increases with petrol consumption" is unsourced, and off the top of my head I can think of several factors (such as increased combustion temperatures at high engine rpms) that could change the speed dependence of total amount of air pollutants emitted.
 * I think that there is a possibility for the article to merit a keep, if we are able to find sources to cover some of the following:
 * Popular misconceptions about the dependence of energy consumption on speed
 * Adjustments that car designers make to control the dependence of energy consumption on speed
 * The effects of speed limits, or other forms of speed control, on roadside pollution, gas consumption etc in certain areas.
 * These would allow the article to instead talk about the way the speed dependence influences other factors, which would not require any synthesis. With a cursory search I have not been able to find any. Fermiboson (talk) 04:22, 28 November 2023 (UTC)
 * @Fermiboson Sorry, but please put these kinds of comments on Talk:Car_speed_and_energy_consumption.
 * If an item in the article is incorrect and unreferenced, correct it or delete it.
 * If an item in the article is incorrect and referenced, find another reference or let it go.
 * If an item in the article is incorrect don't threaten to delete.
 * There are lots of reasons to delete but none of them include incorrect items. Johnjbarton (talk) 16:10, 28 November 2023 (UTC)
 * I'm not arguing that we should delete the article because things are incorrect, I am arguing that we should do so because there is nothing left that isn't either essay or reproduction of information after those things are removed. I pointed out several factual inaccuracies because @Hansmuller asked me to do so on my tp. Fermiboson (talk) 16:18, 28 November 2023 (UTC)
 * I agree with @Fermiboson. My opinion of the article is that it will mislead readers because it only considers the very minor terms, not the big ones. Consider the two main Figures, Graph 1 and Graph 2. From Graph 1 I should drive at 30 km/h or less. From Graph 2 I should drive a Prius at 30 km/h or less, and not buy a BMW which does not obey anything in the article.
 * If I now go to an authoritative source such as https://afdc.energy.gov/data/10312 or the full data at https://tedb.ornl.gov/ a different picture emerges. Three key points:
 * Engine efficiency is not linear, in many cases it increases with speed if we ignore frictional losses, see for instance http://dx.doi.org/10.1088/1757-899X/237/1/012011 (as just a source I pulled quickly).
 * Frictional losses in cars are not speed independent, it is much more complicated than this, see for instance https://doi.org/10.3390/lubricants7050039. This is lubrication science, and not a simple high-school problem. At low speed you can have boundary lubrication; at higher speeds you transition to lower friction and hydrodynamic lubrication, see Stribeck curve. You also have to worry about viscosity changes with engine temperature etc.
 * Rolling resistance is not so simple, see the decent article on it. You can always purchase low rolling resistance tires.
 * We already have a good article at Energy-efficient driving which is far more detailed. I see no reason for this article to exist. Energy efficiency, engine efficiency and lubrication are not simple topics.
 * For fun, something you won't find clearly spelt out here or elsewhere. A few years ago as an experiment a German automobile company worked on a very clean and efficient automobile engine, so there would be no particulates in the engine to lead to wear or frictional losses. The result, horrible. It turned out that they made it so clean that there was no graphitic material being produced inside the engine, and graphitic materials are good solid lubricants. Tribology is complex. Ldm1954 (talk) 00:43, 29 November 2023 (UTC)
 * Your posts with these detailed references make a compelling case that this topic is WP:Notable. Again the accuracy of the article should be discussed in the Talk page.
 * The graph in makes the important point that the graphs that MacKay chose are not the ones that are important to drivers. What counts for drivers is mpg vs speed, not energy vs speed. And the graphs on energy.gov show that the speed effect is much less dramatic once you factor in the miles gained at higher speed.
 * Performance of a small compression ignition engine fuelled by liquified petroleum gas does not seem to be related to the article.
 * The Knauder reference is about engine speed effects, not vehicle speed effect. As you know transmissions cause these to be not equal.
 * The Rolling resistance of tires is approximately constant once you have purchased them. See https://www.trb.org/publications/sr/sr286.pdf
 * I disagree that Energy-efficient driving is a good article. For example, the mpg effect per the energy.gov example is not discussed. It needs work and we should encourage improvements.
 * In my opinion this overall approach of dumping on the article does not improve Wikipedia. Our goal should be better articles and telling editors their work stinks and should be deleted the worst way to accomplish that goal. The most you can accomplish that way is the deletion of one small article that everyone agrees is flawed and driving away the editor. Big deal. If on the other hand you ask what can we do to guide an editor towards better contributions, that editor may go on to make improvements over time. Since all of the dumping takes time I don't see any real cost of a more positive approach. Johnjbarton (talk) 02:56, 29 November 2023 (UTC)
 * We will agree to disagree. I am not an expert on automobiles and lubrication, I have only collaborated with people who are for ~20 years. My focus has been more on nanotribology, so I only know the applied results from conferences and general relevance in papers/proposals. Ldm1954 (talk) 12:10, 29 November 2023 (UTC)


 * Delete. All the encyclopedic material has been merged to Energy-efficient driving, and the redirect is not useful. Jähmefyysikko (talk) 06:21, 5 December 2023 (UTC)


 * The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review). No further edits should be made to this page.