Talk:Exhaust gas/Archive 1

Comments

 * The picture of the truck is ridiculous. 1) diesels rarely blow black smoke at start-up and 2) today's diesels don't smoke at all. Disingenuous depiction of a diesel which seems to indicate an agenda. — Preceding unsigned comment added by 74.111.209.159 (talk) 14:49, 30 September 2011 (UTC)
 * "in regards to the transport truck emitting all the fumes, does it really matter what country its from? im removing the label stating the truck is from the united states because its not relevant." —Preceding unsigned comment added by 207.210.29.97 (talk) 20:22, 20 December 2009 (UTC)
 * "Diesel exhaust has a characteristic smell." Don't all types of fuels have "characteristic smells"?  :-)
 * "relatively harmless carbon dioxide" -- by calling CO2 emissions "relatively harmless", are we making a (non-NPOV) claim about the (in)significance of greenhouse gasses and global warming? 05:46, 1 December 2005 User:71.117.4.58
 * Can anyone tell me why car exhausts smell different in the US compared to here in Australia?Myrtone (the strict Australian wikipedian) 13:46, 29 March 2006 User:Myrtone86
 * Don't you think saying that Carbon Dioxide is "relatively harmless" is a totally stupid idea, it is clearly a harmless gas given the state of the atmosphere 14:13, 4 April 2007 User:82.32.59.53
 * the statement in parentheses "(although carbon dioxide is generally recognized as a greenhouse gas that contributes to global warming)." is incomplete and a disservice to accuracy. Water vapor is mentioned with CO2 as almost equal components of exhaust but its property as the most powerful greenhouse gas is not, which is very misleading.  Suggest something like "(although water vapor, the most powerful greenhouse gas, and carbon dioxide are generally recognized as contributing to global warming)."  — Preceding unsigned comment added by 205.145.19.4 (talk) 16:51, 14 January 2014 (UTC)

Article move
do not move Anthony Appleyard (talk) 21:47, 12 March 2009 (UTC)
 * I moved the article to exhaust plume. I agree that most of the article is currently about exhaust chemistry, nevertheless, the concept of exhaust plume comfortably encompasses chemistry, and the article has plenty of scope for including the shape and other behaviours.
 * I'm therefore proposing to move it back to exhaust plume again, unless anyone can come up with a good argument.- (User) Wolfkeeper (Talk) 14:23, 7 March 2009 (UTC)
 * Exhaust gas → Exhaust plume — This article was at Exhaust gas for a long time, and someone moved it to Exhaust plume, and I moved Exhaust plume back to Exhaust gas because most of the text is about the gas, not the plume shape. Anthony Appleyard (talk) 16:20, 7 March 2009 (UTC)
 * I have listed this move as "to be discussed" in Requested moves. Anthony Appleyard (talk) 16:20, 7 March 2009 (UTC)
 * Most people call it "exhaust gas" or "exhaust fumes", or other names for chimney smoke etc. Google hits are: exhaust gas c.1,550,000; exhaust gases c.599,000; exhaust gasses c.681,000; exhaust fumes c.345,000; exhaust plume c.35,800; exhaust plumes c.19,100. Anthony Appleyard (talk) 16:29, 7 March 2009 (UTC)
 * Comment. I am not an expert in this subject, and I could be persuaded. However, it seems to me that there is a qualitative difference between plume and gas. Exhaust gas is more general, and could be found anywhere. By contrast, a plume is gas concentrated in a particular area, such as a smoke plume rising from a power plant, or the contrail of a jet. It appears to me that this article is more concerned with gas in general than gas in a plume. •••Life of Riley (T–C) 20:44, 7 March 2009 (UTC)
 * No, the exhaust gas is just the gas, the plume includes the gas, the chemistry of the gas, the thermodynamics of the gas, interactions between the gas and the surrounding ambient gas, the shape of the exhaust that forms and any other interactions at all in every possible way, including, potentially, interactions with external objects, including but not limited to weather systems, flora, fauna.- (User) Wolfkeeper (Talk) 21:22, 7 March 2009 (UTC)
 * The plume is merely the shape that the gas sometimes assumes as it gradually disperses downwind. It is the gas that interacts as stated. Anthony Appleyard (talk) 06:25, 8 March 2009 (UTC)
 * Comment shouldn't flue gas be merged here? 76.66.193.90 (talk) 05:49, 9 March 2009 (UTC)
 * Oppose the proponent of the move confirms that the current title describes the current article. It seems the proponent wants to use "plume" in a highly technical sense in order to justify a future expansion of the article content in some unspecified way. To the general reader "exhaust plume" would imply some visible, feather-shaped phenomenon and would be confusing. As the current article discusses particulates in exhaust as well as the gas, perhaps a more appropriate generalisation would be something like Exhaust emissions, or if that was seen as tautological, Exhaust (emission). As a suggestion, perhaps if Wolfkeeper starts a discussion about the plans he seems to imply he has for the page, then a consensus for the page's name may grow naturally out of that. --Rogerb67 (talk) 14:19, 9 March 2009 (UTC)
 * Currently page Exhaust is a disambig of 18 choices. Anthony Appleyard (talk) 17:02, 9 March 2009 (UTC)

Steam engines

 * Quote: "In steam engine terminology the exhaust is steam that is now so low in pressure that it can no longer do useful work". What about coal smoke? Biscuittin (talk) 16:21, 15 October 2009 (UTC)
 * It is called smoke, or flue gas. Steam engine exhaust means spent steam. Anthony Appleyard (talk) 16:52, 15 October 2009 (UTC)
 * Smoke or flue gas is what the article is about. If you want to stick with the definition "Steam engine exhaust means spent steam" then I think steam engines should be excluded from the article. Biscuittin (talk) 19:06, 18 October 2009 (UTC)
 * Quote: "Exhaust gas or flue gas" ... Shouldn't this be "fuel gas" ... ? 213.190.107.34 (talk) 21:49, 19 August 2010 (UTC)
 * It is not a mistype. A flue is a sort of chimney. Anthony Appleyard (talk) 05:52, 26 August 2010 (UTC)

Neutrality
I added the POV template because the article appears to have been created and constrained to restrict the scope to pursue a particular POV. Particularly: -- de Facto (talk). 22:16, 11 April 2010 (UTC)
 * 1) The word 'Car' in the title excludes other, possibly more polluting forms of motor vehicle such as trucks and buses.
 * 2) The lead constrains the article to 'tail pipe emissions' which excludes emissions, possibly more significant and harmful, of vehicles which use off-board, but also polluting systems to supply their energy.
 * 3) The lead constrains the article to 'gasoline' engined cars which excludes the more CO2 efficient diesel engined cars which are common in Europe.
 * 4) The 'pollutants' are listed with their potential ill-effects without indicating the actual risks of the levels emitted.


 * >The word 'Car' in the title excludes other, possibly more polluting forms of motor vehicle such as trucks and buses.

Feel free to create a more generalized article called vehicle pollution.
 * >The lead constrains the article to 'tail pipe emissions' which excludes emissions, possibly more significant and harmful, of vehicles which use off-board, but also polluting systems to supply their energy.

Articles need to have scope. With out scope they get very messy and long. For example should oil spill pollution be added because cars need oil? Should pollution caused by transmission of the fuel to the gas station be part of the article? I feel the article has good scope. It doesn't preclude more generalized articles from being created. On second thought perhaps the scope issue isn't so important on this short article so go ahead and add other forms of pollution and the lead can be changed accordingly.
 * >The lead constrains the article to 'gasoline' engined cars which excludes the more CO2 efficient diesel engined cars which are common in Europe.

You can create a more generalized article if you want and rename this one appropriately. Perhaps rename this article to gasoline car pollution. Alternatively add diesel to this article. Already has a small reference to it. Daniel.Cardenas (talk) 22:53, 11 April 2010 (UTC)
 * >The 'pollutants' are listed with their potential ill-effects without indicating the actual risks of the levels emitted.

Its not POV, it is interesting data and if someone has it, it would be good to add to the article. This article in the external links trys to bring scope to the ill-effects of them. Feel free to try to incorporate the data into the article. Daniel.Cardenas (talk) 22:53, 11 April 2010 (UTC)

Factual accuracy
I added the 'out of date' template because the article does not give the dates for which the presented data applies. Looking at the source of the 'Passenger Cars Emissions' table the data dates back to 2000 - it is 10 years out of date. With current environmental pressures and technology advances the automotive industry has made huge improvements to their emissions over the last 10 years which have not been taken into account. -- de Facto (talk). 22:23, 11 April 2010 (UTC)
 * Do you have a reference for that statement? Otherwise it is just opinion, without fact.  Feel free to add dates to the article. Daniel.Cardenas (talk) 22:39, 11 April 2010 (UTC)

Globalize
I added the 'Globalize' tag to this article because most of the data presented is very specific to the United States and that fact isn't made explicitly clear in the text. -- de Facto (talk). 22:26, 11 April 2010 (UTC)
 * Go ahead and make it explicitly clear or add more global data. The data fetched was what came up first in google search or was copied from other wikipedia articles.  Daniel.Cardenas (talk)


 * Personally I don't see the justification for the globalise tag - the pollution from cars is the same everywhere, indeed the world pretty much uses the cars from the same factories. Could you be more specific about what you want to see changed before the tag is removed? Possibly if the reference format was cleaned up and provided the 'publisher' or 'work' information. Would that be sufficient for you? PeterEastern (talk) 21:29, 25 April 2010 (UTC)
 * The data cited is mostly old U.S. EPA data for the U.S. U.S. cars mix (diesel/gasoline) is not typical, U.S. climate is not typical, U.S. fuel consumption is not typical, U.S. car use and transport mix is not typical.  I've just added some recent European data for CO2. -- de Facto (talk). 21:46, 25 April 2010 (UTC)
 * Thanks for the new EU references. Possibly you will be able to add sufficient international references until you are content to remove the tag? Personally I think it would be fine to remove the tag now but more references from elsewhere and more recent ones would be a bonus. PeterEastern (talk) 21:55, 25 April 2010 (UTC)

Redirected to Air pollution
I have redirected it to Air pollution to solve a lot of problems with this article. As well as the issues mentioned above the name of the article is unsuitable. There is no specific "car pollution" - it is really a "fossil fuel powered vehicle pollution". -- Alan Liefting (talk) - 06:35, 13 April 2010 (UTC)
 * Renamed to Car tail pipe emissions. Daniel.Cardenas (talk) 14:46, 13 April 2010 (UTC)

Adding related info
Because an article has car in the title does not preclude close related info from being added. Especially if that is the way references have listed relevant information for car. Daniel.Cardenas (talk) 00:28, 14 April 2010 (UTC)


 * The added information didn't specify what proportion of the pollution and smog was attributable to cars as opposed to the other forms of transport mentioned, and it didn't take account of the proportion attributable to other non-road transport contributors. For those reasons, its inclusion here likely adds undue weight to the significance of the actual contribution from cars and without reference to the other (bigger) sources it also adds undue weight to the contribution of motor vehicles in general.  Your argument would equally justify the inclusion of coal-fired power generation plants in the lead if you could find a reference mentioning them in the same sentence as cars.  Cars is a subset of motor vehicles not a super-set, and motor vehicles is a sub-set of polluters.  The inclusion of that statement in the lead gives an unbalanced view of the size of the contribution made by cars alone, and so is unacceptable.  You need to find a reference which singles-out the actual significance of the contribution from cars. -- de Facto (talk). 09:28, 14 April 2010 (UTC)
 * No, it has been highly publicized here in the U.S. much of the air pollution comes from the millions of cars. Studies have been done, but you find them unacceptable because they are old. There is a reason that cars are listed first as major produces of smog in the references.   Daniel.Cardenas (talk) 12:49, 14 April 2010 (UTC)
 * Here is a reference saying cars then coal plants are the largest contributors of ozone, if you want to incorporate it into the article: http://blog.al.com/breaking/2010/01/new_ozone_standards_put_cars_t.html . And there are references indicating the major component of smog is ozone. Daniel.Cardenas (talk) 13:10, 14 April 2010 (UTC)

Article title
It seems that the title of this article is being changed each time POV balancing content is added; to deliberately put that new content outside of the scope of the title. First it was titled Car pollution. Then it was changed to Car tail pipe emissions following the inclusion of content referring to forms of pollution other than air pollution. Now its title has been changed again, this time to Car tail pipe pollution, following the inclusion of non-pollutant emissions. Where are we going with this? What is the agenda for this article? -- de Facto (talk). 07:16, 14 April 2010 (UTC)
 * Motivation for this article is to discuss car tail pipe pollution. Original title: Car pollution was too vague.  I thought Car tail pipe emissions was a good title to discuss typically regulated emissions, but unrelated info was added, thus the change to pollution.  There is much debate about electric cars and hybrid cars and this article serves as data for that debate.   Daniel.Cardenas (talk) 12:51, 14 April 2010 (UTC)

In a 2006 publication, the Federal Highway Administration state that in 2002 about 1 per-cent
Where does it say that in the reference? I don't see it.

Daniel.Cardenas (talk) 15:26, 14 April 2010 (UTC)
 * Have you read it all? It's on the "Emissions Trends" page.  Can you find a PDF link for the whole document - it would be easier to reference? -- de Facto (talk). 16:55, 14 April 2010 (UTC)
 * Thanks, restored the text and made the reference point to page ten. I could not find the PDF version.  Daniel.Cardenas (talk) 18:14, 14 April 2010 (UTC)

Beijing image
Was the presence of the Beijing image meant to imply a connection between car tail pipe emissions and the apparent smog? Beijing may well be known for its smog, but what evidence is there that cars (as opposed to other types of road vehicles or non-motor vehicle sources) are responsible in any way for it? This WRI article suggests that the evidence shows that cars are unlikely to be responsible for Beijing's smog. -- de Facto (talk). 21:44, 14 April 2010 (UTC)
 * I see that before I'd finished writing the above comments that the image has already been reinstated, with the edit comment "car exhaust is a major contributor to smog". Then a subsequent edit adds references giving general speculation about smog.  Where is the reference that supports the assertion that cars have a major role in causing Beijing's smog - I don't see it? -- de Facto (talk). 21:54, 14 April 2010 (UTC)
 * The image is about smog, it doesn't matter the location. The second sentence in the article gives the connection between smog and cars emissions. Daniel.Cardenas (talk) 23:32, 14 April 2010 (UTC)

Rename to cover content
As the data isn't readily available for cars only, and as the article currently covers more than just cars anyway, I've renamed it to Motor vehicle tail pipe pollution. -- de Facto (talk). 18:53, 15 April 2010 (UTC)
 * The passenger vehicle data is available from the EPA. I was in the process of collecting that data, but will put it on hold for now. Daniel.Cardenas (talk) 20:00, 15 April 2010 (UTC)
 * Is it there for trucks and buses too? If it is, then include it, as the comparisons will be valuable; or at least put it here so that we can consider it. -- de Facto (talk). 21:36, 15 April 2010 (UTC)
 * The database is provided in mySQL format, so it is not easy to extract. http://www.epa.gov/ttn/chief/net/2008inventory.html#inventorydata   Daniel.Cardenas (talk) 23:05, 15 April 2010 (UTC)

Solvents in text
This article is about Motor vehicle tail pipe pollution, VOC emissions by solvent use is not sufficiently notable for motor vehicle article. Emissions by motor vehicle equipment such as gas stations is sufficiently interesting. Also solvent use is shown the chart next to the text. Daniel.Cardenas (talk) 18:58, 19 April 2010 (UTC)


 * Do you want to widen the scope of the article again to cover types of motor vehicle pollution other than tail pipe emissions? You carefully removed details of other types before when I added them (when the article title was broader) - do you remember this edit of yours?  You even subsequently renamed the article from Car pollution to Car tail pipe emissions (here) to narrow the scope to exclude other types of car pollution.  Gas station emissions are not currently in scope.  The reason that the largest source of VOCs deserves a mention is beacuse the first thing that a reader is going to ask when they see that motor vehicles are the second largest source is: "what's the largest source is then?". -- de Facto (talk). 22:13, 19 April 2010 (UTC)


 * O.k. how does one keep a limited scope while widening it? Call it regulated emissions?  Daniel.Cardenas (talk) 22:37, 19 April 2010 (UTC)


 * Why have the scope limited? Why not cover all emissions resulting from motor vehicle production, use and disposal? -- de Facto (talk). 18:36, 20 April 2010 (UTC)
 * That sounds like a good article, but not one I want to tackle. I'd like to see one that can be used for the debate of a car with emissions versus one that doesn't.  Sounds like the previous title of motor vehicle emissions is the right one.   Daniel.Cardenas (talk) 19:25, 20 April 2010 (UTC)

VOC sources
Here are the reasons for my adjustment of the VOC section details... From the FHWA report you can see that only about half of the VOCs emitted from motor vehicles come from their tail pipes. Currently this article scope is limited to tail pipe emissions, so to only about half of the VOCs emitted from motor vehicles. To imply that any more than about 15% of the total U.S. VOC emissions come from motor vehicle tail pipes is therefore misleading, and to associate VOCs emitted from elsewhere with tail pipe emissions would be disingenuous. We could widen the article's scope to include them. Any views on this? -- de Facto (talk). 22:42, 19 April 2010 (UTC)
 * See section above for how to expand scope. Daniel.Cardenas (talk) 23:36, 19 April 2010 (UTC)

'Environmental impacts of roads' article
I created a new article Environmental impacts of roads from content within the road article and with a stub in the Highway article. It was created at the suggestion of a contributor to the Road article following a discussion of how to rationalise the two articles. Please feel free to contribute to the article which I am unlike to do much more with. PeterEastern (talk) 14:05, 25 April 2010 (UTC)

CO2 and climate change - fact or theory
When is something deemed to be 'true' in Wikipedia. Is CO2 "part of the anthropogenic contribution to the growth of CO2 concentrations in the atmosphere which is believed by a majority of scientists to play a significant part in climate change" (as described by DeFacto showing a significant element of doubt on the matter) or "are an important contributor to the growth of CO2 concentrations in the atmosphere and therefore to global warming" (as per User:John Quiggin's edit which doesn't display any doubt) or "is a non-toxic greenhouse gas; the emissions are attributed to global warming." (as it was before John Quiggin's edit which has a different spin again)? This is not something that should have to be debated on this page and I assume that broader guidance on available - Possibly someone can point out the policy on this topic. PeterEastern (talk) 21:43, 25 April 2010 (UTC)


 * WP:WEIGHT is the main guideline here. In a brief mention like that we have here, we should go with the scientific consensus on global warming. If the section is expanded, it would be appropriate to mention minority views, to the extent they are relevant to the article topic, while making it clear that they are minority views. Similarly, in an expanded section, it might be worth a more detailed exposition of the toxicity issue, making it clear that CO2 is not toxic in the concentrations present in the atmosphere from natural and human sources. My other problem with the text I edited was that it had the causation the wrong way around. No one (I think) attributes emissions to global warming; rather, climate change is attributed to emissions from cars and other sources.JQ (talk) 23:18, 25 April 2010 (UTC)

Undue weight...
I am watching with interest the replay of the arguments I had with DeFacto on Overspill parking where we argued (and are still arguing) over the caption for a photo. It is of course good to achieve balance, but not an the expense of loosing the core message. Whether the part of the exhaust one can see if good for one or not is beside then point and I think the article has much more meaning with the single original photo. I find myself imagining an article about someone who was poisoned by an arsenic laden sandwich having the sandwich described as being 'all natural ingredients', 'fresh local organic produce', 'nutritious' and '99.9% healthy'. The relevant fact was of course that the last 0.1% was lethal - the rest of the recipe is not notable. PeterEastern (talk) 12:35, 28 April 2010 (UTC)


 * Perhaps a compromise is in order. Mentioning that sewage is 99% water is perhaps helpful to the reader. Daniel.Cardenas (talk) 16:49, 28 April 2010 (UTC)


 * Daniel, do most cars smoke like that for most of their journeys where you come from? Do even 50% of cars smoke like that?  If the answer to that last question is no, then by, not only adding the image back into the article, but by also putting ahead of the more representative image, you are surely giving it undue weight.  I would respectfully suggest that you re-remove it. -- de Facto (talk). 20:19, 28 April 2010 (UTC)
 * This article is about emissions, and the image illustrates emissions. An anology is the field lines shown in magnetic articles.  Do field lines exist?  No, but they are there to show what is being talked about.   Daniel.Cardenas (talk) 20:45, 28 April 2010 (UTC)


 * Peter, what was you motivation for writing that message - was it purely to discuss ways to improve this article, or was there an ulterior motive? My point about the original photo here is that it is not representative of typical real-world examples.  It appears to have been selected, as you intimated, to present a "core message".  As we know, Wikipedia is not a soapbox and exaggeration (even in photographs) is not conducive to achieving a neutral POV balance in the article.  That exhaust gases from most cars on the road are virtually invisible is a fact, not a personal opinion, so is not subject to compromise or negotiation.  You named this section "Undue weight..."; were you thinking what I'm thinking; that that is precisely what the old image had been given - it was giving undue weight to the notion that car exhaust looks like grey-coloured smoke? -- de Facto (talk). 20:11, 28 April 2010 (UTC)


 * This is too silly for words, and reflects a pattern of POV-pushing contributions on a wide range of motoring-related articles. You would not seriously contest the fact that motor vehicle exhaust emissions present a wide range of environmental problems, but you continually edit to imply this, and similarly across many other articles. You are just disrupting the project, and will get nowhere.JQ (talk) 10:08, 29 April 2010 (UTC)


 * I note the further edits to images and order of images. Can I suggest that some "core message" issues are going to need to be resolved before this article settles. My experience with the caption of a photo on overspill parking is that people could spend a huge amount of time of this subject without getting anywhere. Personally I would recommend that anyone who is unhappy with the article shoves a 'neutrality' tag on it and then uses their time more productively on other articles until the underlying issues are unpicked. PeterEastern (talk) 11:06, 29 April 2010 (UTC)

Lead photo
The first image shows a picture of steam—not smoke—being emitted from a tailpipe. It is very obviously steam, and not only does the creator of the image agree (see File:Exhaust.jpg) but asking for a citation on that point is akin to disingenuously obdurate behaviour of the type that does not improve articles. One might as well demand a citation for each of the vague, sloppily written, and technically incorrect words in the previous caption; it read Appearance of car exhaust on a poorly maintained or cold-running car.. A car might emit smoke from the tailpipe. It would be black smoke if the engine were running too rich, blue smoke if the engine were burning oil, grey smoke if the engine were burning transmission fluid (as could happen on some past models if the transmission's vacuum modulator were to rupture). White smoke is also possible, if a cylinder head has cracked or a cylinder head gasket has failed and the engine is burning coolant. reliable citations are available for all of this if you insist. Smoke and steam have characteristic appearances that differ from each other substantially enough to be easily differentiable by casual observation. Because smoke is made of particulates, it has a much wider, more gradual dispersion pattern; steam is made of water droplets and so vanishes much closer to its source—this makes the edges of the steam plume much more clearly defined than the edges of a smoke plume. You may demonstrate this to yourself in any of numerous ways; boil a pot of water on one stove burner and burn some cooking oil in another pot on the adjacent burner, or introduce some oil to the intake tract of a running vehicle and observe the smoke plume from the tailpipe and compare that to the steam plume of the same car emitting steam.

Back to the lead photo: there is no basis for the claim that the depicted car is poorly maintained. Even if the picture showed a smoking (rather than steaming) tailpipe, there's still no basis for saying the car is poorly maintained, for it could be a very well maintained car that is simply worn out. Moreover, water is one of the main constituents of engine exhaust, and a brand-new, perfect automobile will emit steam from the tailpipe for a brief period when the exhaust system is cold, and steadily when the ambient temperature is low enough to cause condensation. We humans also emit steam when we exhale under similar conditions. It is not accurate to say the photo shows a "cold-running" engine; an engine that does not attain normal operating temperature (as for example because of a faulty coolant thermostat) will not emit more steam than an engine at normal operating temperature. The caption I've replaced this mess with is a much more accurate description of the photo, but the photo itself is a poor choice for this article.

Rather than squabbling about captions for a photo of marginal relevance to the article's subject matter, let's coöperate to find (or produce) a photo of better relevance. It's growing more difficult to find smoking cars to photograph, as emission regulations for vehicles in use have grown stricter. However, it still ought to be possible sooner or later to find and photograph such a vehicle, and then the caption will almost write itself. For now, an accurate caption on a sub-optimal photo is better than a poor caption on a sub-optimal photo. —Scheinwerfermann T·C 20:43, 24 May 2011 (UTC)
 * What makes it obviously steam? The basis for poorly maintained is obviously that poorly maintained cars emit smoke. Daniel.Cardenas (talk) 20:49, 24 May 2011 (UTC)
 * I will be glad to have this discussion with you. I started, and now it's your turn to read what I wrote and engage with the points I raised. Your one-line response amounts to "Is not! Prove it!", which is neither productive nor responsive. Moreover, it is not necessarily the case that poorly-maintained cars emit smoke. Many poorly-maintained cars do not. I will refrain from asking you for reliable support to verify your assertion that poorly-maintained cars "obviously" emit smoke, because that would be petty and not constructive. Let's not lose sight of the objective, which is to improve the article. —Scheinwerfermann T&middot;C 20:59, 24 May 2011 (UTC)