Talk:Motor oil

viscosity teperature

"The first number '10W' is the viscosity of the oil at cold temperature and the second number is the viscosity at 100 °C"

any chance we could find out the temperature? here http://www.waynesgarage.com/docs/oil_facts.htm says 0c . — Preceding unsigned comment added by 165.86.81.22 (talk) 06:58, 4 June 2014 (UTC)

Links

There are no links in this article. I am new to this, but may attempt to cross reference key words.

Go for it! By the way, it's best form to sign your posts, by typing four tildes ~~~~ -- this turns into your name and time: Coneslayer 01:26, 2005 May 19 (UTC)

Since the above initial comment, many links have been added and many other edits made to this article. A few new sections and some more information have also been added. The article is in significantly better shape now. H Padleckas 17:47, 16 July 2006 (UTC)

Article not practically finished yet

I have n't practically finished this article yet. I will modify modified the "Uses" section for certain mechanical corrections and I will add added a new "Synthetic Oil and Synthetic Blend" section and new a "Non-vehicle uses" section. Both have been written offline. I just haven't gotten to putting them in yet. H Padleckas 03:25, 19 May 2005 (UTC)
H Padleckas 17:47, 16 July 2006 (UTC)

• Does anyone know what API Standard number defines the service categories for Gasoline and Diesel engines?

http://www.burkeoil.com/pdf/oilguide.pdf

Length of article

The article looks pretty good now. However, it has reached 30 kb in length, which is considered a little long by Wikipedia standards. Does anybody think the "Common Points of Discussion" section at the end is really necessary or unnecessary in this article? H Padleckas 17:04, 2 August 2006 (UTC)

This section has been removed by now. H Padleckas 04:37, 20 May 2007 (UTC)

==Question== I put a quart of transmission fluid in my engine last night instead of engine oil!

Can someone please tell me what will happen? Do I have to get it drained? I already drove about 10 miles, have I cause permanent damage?

Help! Desiree

You are more likely to get an answer to any questions you have by posting on the Reference desk. Either the science or miscellany section will be suitable. I'm not an expert on this issue, but I imagine that you will need to drain it, transmission fluid is not designed as a lubricant Lurker ^haver 13:55, 12 August 2006 (UTC)

You should draine it and refill it with proper engin oil as soon as posiblie. The atf fluid is far better then nothing but is far from ideal.

Wow - is there an engineer in the house? I'm sorry, I'm not usually slanderous in Wikipedia - but come on - does anyone on this page know what he or she is talking about? "...transmission fluid is not designed as a lubricant..."? Please people - this is not a forum, this is an article. Please don't post information that is not backed up or cited from a reputable source, or so obviously untrue (I happen to know that transmission fluid is indeed a lubricant, as it was designed to be). Go to a forum or something of that nature to determine what you should do. No one would call up Encyclopedia Britannica and ask them what to do about your engine oil problem; this is not the place for such discussion. Also, please sign your posts. Behavior such as this is what hurts the credibility of Wikipedia. Nicholas SL Smith 16:23, 7 September 2007 (UTC)

motors

I've again disambiguated this page so that it doesn't directly link to Motors. This article is about internal combustion engines with only one sentence mentioning electric generators. A bit of research confirms [1] that electric motors normally are air cooled, and lubricate their bearings using grease and not motor oil. (Unless they're used as liquid pumps, where the pumped media will carry away heat. This is also the case in large-scale generators.) -- Mikeblas 14:34, 12 August 2006 (UTC)

Their is a part on the page that says that more wear occurs in the engine between 1000 and 2000 miles. I find this to be completely erroneous for my experiences as a mechanic is that customers who always change their oil at three thousand never have internal engine problems like bearings wearing out or becoming noisy even at three and four hundred thousand miles were as those who are trying t be cheap and wait for to eight thousand far more often run have internal engine noise due to play in the bearings. And are their cars typically burn oil run out and throw rods. Now this is just my experience but I have seen no founding for the assertions made on the page. I could accept what is said if it were properly sighted by several verifiable sources. Also while the automotive industry my push 3000 mile oil changes the cost of an oil change at 35 dollars is very little compared to the cost of engine replacement. used engine cost being (for "low mileage 30-40k" pre removed) 1500-8000 depending on vehicle atypical Toyota Camry would be about 1500 and labor for a Toyota Camry would be about 15 hours at 75$ plus an hour this will only increase in cost as the size of the engine increases v6 v8 and on mini vans it would be much more than 15 hours. So while it might be a little premature it does no harm and it does not save you anything to change the oil less often.

oil changing company conspiracy

I removed the following text for lack of references or citations. Content must be verifiable.

For example, most people in the United States believe that a common oil change frequency should be every 3000 miles or every 3 months, whichever comes sooner. This 3000 mile oil change interval has been relentlessly promoted by oil changing companies for decades. It had a scientific basis when engines used non-multi-weight, non-detergent oil. It no longer has any scientific basis, but it is still being promoted by certain entities, most notably the oil change industry in the United States (including car dealerships). Indeed, studies have shown more wear occurs with fresher (1000-2000 mile) oil. This is attributed to additives re-establishing themselves, TBN converging, and filters becoming more efficient. Most manufacturers recommend oil change intervals of 6,000 miles or more for modern cars. In Europe, by contrast, where the influence of oil companies has been much less, oil is typically changed only at a major service interval, between 10,000 and 15,000 miles for a modern car. For convenience, the oil filter is usually also replaced at the time the oil is changed.

--Ibanix 19:47, 28 December 2006 (UTC)

There is still a large section of text that is linked to "http://www.nordicgroup.us/oil.htm". Someone needs to provide a proper link or remove it. I wonder how much of this article is directly from this text.

Types of Cheap Oil

Something that I think might be interesting for the article would be information about the different types of oil you can buy and whether or not they'll actually affect your car that much. I mean, I've got a 1994 Ford Fiesta (classic), done about 70,000 miles and I'm wondering whether I should buy the cheapest oil possible or something a little bit better. I heard that it makes no difference when you've got an old car but then it says on the container the cheapest oil comes in that it's for cars with 100,000+ miles on the clock, so I figured I'd be better off with the slightly better stuff. You know, on the cheapest oil, it's described as "motor oil" whereas the slightly better stuff is described as "petrol oil". Doom jester 11:32, 14 March 2007 (UTC)

Needs cleanup

This article needs help with basic grammar, spelling, proper headings, and encyclopedic tone. --Charles Gaudette 09:55, 18 April 2007 (UTC)

How to change the oil in your car

This Motor oil article was already somewhat long when a new "How to change the oil in your car" section was recently added, making it even longer (about 36K). Even before the addition of this new section, the "Maintenance" section provided an overview about motor oil replacement in a vehicle in order to provide a basic understanding of how it's done. This new section includes a detailed step-by-step practical procedure on how to change the oil in one's vehicle, including such advice as wearing old jeans, not screwing in a new oil filter too tight, etc.

According to Section 1.8.4 of What Wikipedia is not, Wikipedia articles are not Instruction Manuals (how-to guides). Wikipedia is not the place for detailed step-by-step procedures such as the "How to change the oil in your car" section just added. This how-to procedure section has since been removed and is now available only in previous revisions under history. However, there is a Wikia called Wikihowto for such how-to procedures. This how-to section (now only in previous revisions under history) for changing your car oil can be moved to Wikihowto and the section in the Motor oil article replaced with given an external link leading to it. Of course, when the procedure has been moved to Wikihowto, it can have an external link to the Wikipedia Motor oil article. H Padleckas 17:24, 11 May 2007 (UTC) H Padleckas 04:10, 20 May 2007 (UTC)

In another website called WikiHow, there is an existing how-to procedure called "How to Change the Oil in Your Car." An external link to this WikiHow procedure has been placed in the "Maintenance" section. H Padleckas 04:45, 20 May 2007 (UTC)

This Talk section modified yet again to take Wikihowto into account. H Padleckas 12:10, 21 May 2007 (UTC)

I've deleted most of the "how to" stuff, and merely placed the WikiHow link at the bottom. I do think the "reason" why you need to change engine oil is still valid, hence why I left it in. -- Teutonic Tamer 18:23, 19 December 2007 (UTC)

3000 miles myth/fact

These sections seem to be plagiarized from this page: http://www.nordicgroup.us/oil.htm

Removed Copyvio 208.124.27.242 21:46, 25 May 2007 (UTC)

Multi-Grade Oils

I find the below text to be rather confusing. Is that supposed to mean the oil can be pumped at a lower temp on startup or at operating temp?

The API/SAE designation for multi-grade oils includes two grade numbers; for example, 10W-30 designates a common multi-grade oil. The first number associated with the W (again 'W' is for Winter, not Weight) is not rated at any single temperature. The "10W" means that this oil can be pumped by your engine as well as a single-grade SAE 10 oil can be pumped. "5W" can be pumped at a lower temperature than "10W". "0W" can be pumped at a lower temperature than "5W"

--Jkoether 16:02, 22 May 2007 (UTC)

Single-Grade Oils

• Likewise, for "Single Grade Oils" I could not understand if a lower SAE number entails a lower temperature and a higher viscosity, or what. There is no clear association that I could discern. I had to go somewhere else for clarification. I understood that a denser oil freezes sooner, but that's about it. Daniel. — Preceding unsigned comment added by 190.194.237.249 (talk) 02:45, 15 July 2011 (UTC)

"Motor" vs. "engine"

The article comments:

Motor oil used for vehicle engines is commonly called engine oil in American Petroleum Institute (API) documentation.

As far as I can remember I've always heard the substance called "engine oil" rather than "motor oil". It seems to me that "motor oil" is the American term, while "engine oil" is the British term, which happens also to be used by the API. If this is the case, it's probably worth mentioning the alternative name in the lead section. The term "engine oil" is also used a couple of times outside this section without definition. Hairy Dude 21:41, 3 July 2007 (UTC)

Added engine oil in the initial paragraph. -- Teutonic Tamer 18:28, 19 December 2007 (UTC)

Biodegradable Motor Oil Section Has Erroneous Assumption About Disposal

The benefit of this new form of motor oil is the ability to transform the oil back into soil with no negative environmental effects.

That is an erroneous statement. Used motor oil (traditional, synthetic, or biodegradable) contains heavy metals and other contaminants due to the combustion and wear processes. Thus, it cannot be directly disposed of as if it were an innocuous substance. In my opinion, the quoted claim above should be deleted. Shawn D. (talk) 11:32, 17 March 2008 (UTC)

Agree. I have rewritten that part so as not to lead people to just dump their oil out on the ground. Also maybe we should add a section about proper disposal of all types of motor oil. I looked around a bit on the recycling articles for a page to link to, but i think this is something that just need to be written from scratch. Quickmythril (talk) 21:33, 17 March 2008 (UTC)

Dino oil?

The term "dino oil" is not defined in the article, not mentioning the fact that this is not really a term, but just a teenager's slang. What is it doing in the Wikipedia article? —Preceding unsigned comment added by 76.102.249.143 (talk) 03:09, 23 May 2008 (UTC)

Synthetic Oils

Today, synthetic lubricants are available for use in modern automobiles on nearly all lubricated components, allegedly with superior performance and longevity as compared to non-synthetic alternatives. Some tests have shown that fully synthetic oil is superior to conventional oil in many respects, providing better engine protection, performance, and better flow in cold starts than petroleum-based motor oil. These "tests" simply test the parameters of the oil itself and not really how well they work. Synthetics may offer little or no real-world benefit, as witnessed by the millions and millions of cars that lead long lives on plain motor oil. Generally, other components will fail long before the engine dies of an oil-related failure. Lab analysis of the wear metals contained in the used oil show identical or even lower wear with plain dino oils. Consumer Reports attempted to demonstrate the conventional vs synthetic advantages, but chose taxi cabs as a test-bed, which is actually a non-demanding application since the oil stays hot all the time, easily driving off accumulated water and fuels. This "test" in low-performance engines over a less-demanding driving cycle technically proved little about the subject.

I move this here because of lack of citations and POV issues. --THE FOUNDERS INTENT ^TALK 12:28, 29 May 2008 (UTC)

Images

The image at the top of the page should not have a container of a brand name in it. Propose it be replaced with generic image. Undo advertisement. --THE FOUNDERS INTENT ^TALK 17:40, 8 June 2008 (UTC)

The image can be modified to blank out the brand name. H Padleckas (talk) 21:07, 17 August 2009 (UTC)

I just removed the brand name and re-inserted the picture. This article does not have many pictures in it. H Padleckas (talk) 23:11, 17 August 2009 (UTC)

I reinserted the branded bottle, they're wellknown and it can't be considered an advertisement. 109.58.56.96 (talk) 19:49, 25 April 2010 (UTC)

Synthetic lubricants

Synthetic lubricants are designed for "long life" extended drain intervals, but most users rarely run them long enough to gain a cost-effective return. If a "synthetic" oil costs 2 to 3 times as much as a conventional oil, it would have to be used for 2 to 3 times longer than a conventional oil just to break even.

Based on what kind of analysis? wdl —Preceding unsigned comment added by 24.146.23.84 (talk) 19:49, 6 July 2008 (UTC)

The comment "Synthetic lubricants are designed for "long life" extended drain intervals" is not a universally true; some are designed for (and more are advertised/marketed as if they were designed for) Motor Racing in which short drain intervals, but relatively high instantaneous loadings, are the norm.

Mark w69 (talk) 13:10, 2 December 2008 (UTC)

small two cycle

or fuel, often in a gasoline: oil ratio of 50:1, and burned in use along with the gasoline.

often in a gasoline: oil ratio of 50:1, and carburated along with the gasoline.wdl —Preceding unsigned comment added by 24.146.23.84 (talk) 20:07, 6 July 2008 (UTC)

Oil change shops

I suggest include information about oil change shops . --Nukeless 12:29, 22 August 2008 (UTC)

Motor Oil Ltda.

Motor Oil es una empresa dedicada a la comercialización de Aceites y Lubricantes el pais de Chile.

Su sitio web es http://www.motoroil.cl siendo atendido por sus propios dueños. Ernesto Montenegro es Ingeniero Mecanico de la Pontificia Universidad Catolica de Varlaraiso y es In geniero en Mecanica Automotriz de La Universidad Tecnologicade Chie. El junto a su padre han formado Motor Oil Ltda. —Preceding unsigned comment added by 190.20.154.116 (talk) 03:23, 8 June 2009 (UTC)

Viscosity examples/grades

There should be a numerical indication of the range of viscosities for engine oils generally, and perhaps for selected important 'grades'. —DIV (128.250.247.158 (talk)) —Preceding undated comment added 03:00, 17 August 2009 (UTC).

Motor Oil - ???

Having read the article on Motor Oil, it is quite interesting but doesn't help much. If anyone can help me with the following, it will be much appreciated.

When a car manufacturer specified 10w-40 motor oil for its particular model of car. Can 5w-50 be used instead? The logic of it is 5w-50 supposed to be "better" than 10w-40 as it keeps its viscosity at higher temperature (the number 50) and has a "better" low temperature starting property (the number 5w) —Preceding unsigned comment added by 300c-crd (talk • contribs) 03:46, 4 January 2010 (UTC)

This article has quite a few issues; a major one being the long ramblings about non-motor oils and uses in other types of motors. This is layman's thinking. A motor oil is to be in any type of internal combustion engine whether gasoline or diesel, whether 4-cycle or 2-cycle. I already reduced the section on ATF and gear oils, because it's unrelated to this article, so only small mention is warranted. --THE FOUNDERS INTENT ^PRAISE _{GOOD WORKS} 17:23, 14 September 2010 (UTC)

Oil specifications

There is a site out there called www.oilspecifications.org which I think would deserve a link under the External links section. In my opinion it is the single most comprehensive site on the web about oil specifications. There is no other free source where you could find all this information in one place. Even though I added it, it was removed with an explanation (spam) I don't agree with. I definitely don't want to add it again, because I don't want to violate any rules of this site. But, if someone who considers him/herself a lubricant specialist and has the appropriate privileges to add the link again and agrees with me that this site deserves a link here should do it.

The current external links do require some attention though. First of all the link to the ACEA European Oil Sequences is outdated. The current version should be 2008 not 2007. The link called 'A PDF table of motor oil technical specifications' is very far from being useful to anyone except to someone who may want to compile statistics of the motor oils. It contains only raw data about certain oils nothing else. Also it is probably made available against the intent of its author who starts the document with the following: "Thank you for your purchase of “No More Oil Change s: The Motor Oil Bible”. As a special bonus for your purchase, you've been given access to this technical specification comparison document.".

So concluding the things I wanted to say I feel that the site I linked in is relevant, is not in violation of any copyright, it does not sell anything and is closely related to the subject of the article. I am fully aware that Wikipedia is not a directory service and just because a site exists it doesn't deserve a link, but as a lubricant professional I strongly feel that if only a few sites deserves a link there, this one should be among them. If other editors have a different opinion I would be more than happy to discuss it.

--Pkarsai (talk) 17:47, 20 February 2010 (UTC)

Over exuberant rollback on 20th October 2010

I believe "The Founders Intent" has been over exuberant with the rollback on 20th October 2010.

Moving paragraphs will usually make the changes (in history) look substantial by virtue of entire moved or reordered paragraphes being highlighted in red in "View History".

I don't think whoever did the rollback actually took the trouble to analyse the changes and read the new laid out section thoroughly before rollingback and commenting "reverted unsubstantiated mass content removal that should be discussed first."

'S' or 'C'

Article says: -- S for "service" (typical passenger cars and light trucks using gasoline engines), and C for "commercial" (typical diesel equipment --.

Does not the 'S' stand for 'spark' ignition and the 'C' for 'compression' ignition? Sounds more likely than service/commercial. AMCKen (talk) 19:24, 31 August 2011 (UTC)

As stated on API's own website, S does in fact indicate Service, and C Commercial. I agree spark and compression make more sense, but here it is: http://www.api.org/certifications/engineoil/categories/upload/MOTOR_OIL_GUIDE_2010_120210.pdf — Preceding unsigned comment added by Worm12ga (talk • contribs) 01:42, 9 January 2012 (UTC)

W means Winter?

So everyone I know and people on Yahoo! Answers seem to be under the impression that W means "weight" and not "winter." Example: 10W-40 oil means that it's for use in Winter? Given the vague description given in this article, that seems to be the case. Could someone give a better reason for this, and a more specific description, and perhaps a source if it's not too big of an inconvenience? Thanks!

Doubledragons (talk) 04:34, 25 May 2012 (UTC)

Maybe you can find a history of "multigrade oil" that explains this?

Old, non-multigrade oils, were graded by their viscosity and given a single number. They had the same standard number all year, but their actual viscosity changed with temperature. This meant that in the Winter they'd be too thick and it was difficult to start the engine. So oil (which didn't last so long anyway) had to be changed for the season. An oil with a different number was used, to achieve similar viscosities at different temperatures, and to allow the engine to start in the winter. I think (but I'm not sure) that the thin winter oils of 20 grade or so might have been labelled as 20W to emphasise that they were a Winter oil, compared to Summer 50 grade.

This wasn't ideal. It required seasonal oil changes. It also meant that a winter oil, once it reached the engine's operating temperature (which should be constant across the year, maintained by the thermostat) would now be too thin, and might not serve to lubricate to well.

The solution was multigrade oils, which appeared for domestic retail in the 1960s. These have complicated chemistry so that they maintain a similar viscosity across a wide temperature range. In a way they're less "multigrade" and more "un-grade". One of these oils will work equally well in Winter or Summer.

To sell the multigrade oils, to a market that had previously been used to buying two grades of oil, they were labelled as "multi-grade". Rather than emphasising what they really did (maintaining the same viscosity across different temperatures) they were sold in a more recognisable way as "an oil that does the job of two previous oil grades".

Later developments in oils and engines (late 1980s?) allowed thinner oils in general. These thin oils resisted breaking down as well as old heavier oils did, so that a lighter oil could now be used (with obvious benefits of fuel saving from an easier-turning engine), without the oil failing too soon. A 20W-50 might become a 10W-40, or even a 5W-40. Thin racing oils had been used for a long time, but they needed frequent changes.

Old car engines (1950s) use whitemetal bearings with larger clearances than thin wall bearings do. These still need thick oils, so that they can build up the same pressure (to support bearing load) across a thicker oil film in a great gap. Andy Dingley (talk) 10:51, 25 May 2012 (UTC)

In 50 words or less, with a link, why does W mean "winter" and not "weight." Doubledragons (talk) 16:31, 29 May 2012 (UTC)

Because those grades are defined by the SAE (Society of Automotive Engineers.) They have 11 grades, and 6 of them are for winter use and carry the "W" designator. For more, look here [2]. Sperril (talk) 12:06, 9 July 2012 (UTC)

JASO MA and MB explained

I recently wrote an article about JASO MA and MB specifications: http://www.oilspecifications.org/articles/JASO_MA_JASO_MB.php If anyone finds it worthy of being linked to from the article page then please do so. Pkarsai (talk) 10:00, 19 August 2012 (UTC)

Grade

The section on grade needs some beefing up. The line about gear oils seems to contradict the line about Kinematic viscosity regarding the relationship between flow rate and viscosity number. If the gear oil rating is different, it should be explained so the reader understands the difference between rating motor oil and gear oil. --THE FOUNDERS INTENT ^PRAISE 11:49, 21 March 2013 (UTC)

Tables

Does anyone have access to the J300 tables for winter and summer grades? It would be interesting to see.

2 oopses

> Some applications make use of lighter products such as WD-40, when a lighter oil is desired

Wrongly, as WD40 is not a lubricant. Its nearly 100% white spirit with just a little mineral oil

> Most motor oils are made from a heavier, thicker petroleum hydrocarbon base stock derived from crude oil,

heavier than what? 82.31.66.207 (talk) 22:52, 29 April 2014 (UTC)

Heavier (less volatile) than other petroleum hydrocarbon base stocks derived from crude oil....H Padleckas (talk) 18:20, 4 June 2014 (UTC)

Multi grade: confusion

According to the article, 10W-30 means viscosity 10 units at 0 degrees Celsius, 30 units at 100 degrees Celsius. This does not make sense. The viscosity gets lower at higher temperatures, not higher ! If it takes 10 seconds for some amount of oil to flow through a standard orifice at 0 degrees, it must take less, not more at 100 degrees. — Preceding unsigned comment added by 204.193.115.5 (talk) 02:28, 22 October 2014 (UTC)

Tag for "motor oil" in beta editing vandalized

I just noticed that while editing in beta, when you go to create a link to Motor oil, the little blurb that supposed to summarize the page so you know you're clicking on the right article reads "Motor oil: when people are messing with electricity, they can die". It only appears when editing, however; when you turn on the little "preview tag" function, that shows up as the proper text. I'm not sure how to edit either one of these, but I assume it can be done. It's not as bad as vandalism on a "public" place, but they have those little text blurbs next to the article name for a good reason, and that reason is not to screw around. If someone who knows how to would fix this, I'd appreciate it. I'd also love to know how it's done so I can do it myself next time, if you have a second to explain it to me..45Colt 01:33, 15 August 2015 (UTC)

It's still there and it's on the main mobile site as well. — Preceding unsigned comment added by 172.56.13.140 (talk) 04:51, 21 March 2016 (UTC)

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SAPS

We have no mention of "sulphated ash, phosphorus and sulphur" (SAPS) which is an essential property/classification for selecting the correct oil for engines with diesel particulate filters ie. C1, C2, C3 vs A5, B... etc. Widefox; talk 00:07, 30 May 2018 (UTC)

With respect, no it isn't. It is important for oil formulators to know and to tailor formulations to meet OEM and industry specifications within the chemical limits that they define, but the public don't need to know nor care about SAPS so long as they use an appropriately-specified oil. If your car has a DPF the OEM will define which oil specification to look for (perhaps ACEA C3, VW 507 00, BMW Longlife 04 etc). The SAPS limits are built into those specifications so you can choose one with confidence without having to think about what sulphated ash is or why it is important. Here is not the place to walk through all the specifications and lay out what they all require in terms of SAPS, HTHS or the myriad other important requirements. Weasley one (talk) 15:09, 27 September 2019 (UTC)

Cold oil = less viscous?

The article says: Kinematic viscosity is graded by measuring the time it takes for a standard amount of oil to flow through a standard orifice at standard temperatures. The longer it takes, the higher the viscosity and thus the higher the SAE code. Larger numbers are thicker. But it also says: Oil additive technology was introduced that allowed oils to thin more slowly (i.e. to retain a higher viscosity index); this allowed selection of a thinner oil to start with, e.g. "SAE 15W-30", a product that acts like an SAE 15 at cold temperatures (15W for winter) and like an SAE 30 at 100°C. Since SAE 30 is thicker than SAE 15, does this mean that a SAE 15W-30 oil will be thinner at cold temperatures but will be thicker (more viscous) at high temperatures? This seems counterintuitive. - Brian Kendig (talk) 21:10, 24 July 2018 (UTC)

Yes (as literally written). But not in the way you might be reading it.

An ideal oil has consistent viscosity at all temperatures. We don't want the viscosity to change.

A real oil does change - it gets thinner when hot.

So pre-multigrade oils, they were characterised with a viscosity index (one number, maybe 50) and had a useful viscosity when hot. But when it's cold, it's too thick. And in the winter, you have to take it right out and put a thinner grade winter oil in, or else you'll never get the engine started. And that winter oil will still be thick to start, and thinner than ideal once warm.

Enter multigrades. They change their viscosity less. So a 1960s one might pass the summer standard for a 50 weight oil, and the winter standard as if it were a 20W. When cold, it will have the viscosity of a 20W and when hot it will have the viscosity of a 50 - which is less than that of a cold 20W (the heat makes enough difference that it's still the dominant factor), but more (good) than a 20W warmed to operating temperature. And best of all, it reduces the viscosity change enough that you can leave the same oil in year round.

Your SAE 15W-30 won't become more viscous when hot, but it will lose less viscosity, thus behaving as if it had been a heavier grade when cold.

Making the viscosity more stable also avoided the problem of oils becoming too thin when hot, and allowing an oil of a thinner grade to be used (because it won't lose too much viscosity when hot). So over 40 years of changing oil, I've gone from using 20W/50 to 5W/30, which gives less resistance to turning the engine, so saves fuel. I also don't have as many oil coolers as I used to find essential. Andy Dingley (talk) 21:34, 24 July 2018 (UTC)

Which way is up?

I've read through this, and while it's a fascinating dissertation into the uses and history of lubrication something is missing.

AFAICT nowhere does it say whether an SAE30 oil is thicker or thinner than and SAE40 one.

I _think_ a bigger number is thicker - but it's not obvious. Number774 (talk) 21:53, 17 December 2018 (UTC)

Future

The "Future" section, up to the paragraph that describes treatment of polyethylene, reads like an advertisement, or a promotional brochure, and I daresay that is what it is. It does not really contain any information about motor oil as such. It is mainly a collection of incoherent buzzwords, briefly mentioning but not explaining any of them. For those two reasons alone, it does not belong in Wikipedia, however, if more reasons for deletion are required...

What is an "enhanced hydrodynamic circuit", and where is it applied? It is patented, so it is not a trade secret. How could it automatically summon bulk oil pickup? Is it really that difficult for the mechanic to call them him/herself when the drum is full? Where do solar charged lithium batteries fit into this scheme? How does oil re-refining "complete the circular ecosystem system", and does that actually mean something? There is nothing futuristic or inexpensive about "An inexpensive interval (5-7,000kl) oil change at your local Auto store". Most cars specify 10 - 15,000 km intervals. There is nothing stopping the changing of oil without changing the filter with current techniques. The main difference, hidden in all the jargon, and not directly mentioned or explained, is (I think) that they suck the old oil out by inserting a tube into the dipstick tube. Good idea, but not exactly earth-shattering, and as I said above, it has no place in an article about motor oil as a substance. At least I try (talk) 13:08, 18 March 2020 (UTC)