A friend of mine said that he could apparently get better mileage using Chevron oil instead of Shell's (and other brands). Is there any substance to this claim?

  • Hi, Nano! We expect claims to have at least some notoriety before asking folks to spend time researching them... Can you dig up a source for this that indicates a reasonable number of people actually believe it? Can't help but notice that Chevron doesn't seem to be making this claim... – Shog9 Jul 10 '11 at 23:44
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    Many brands have specific claims, eg Shell's claims on getting up to 1.5 times further than other brands, but I don't see one from Chevron. Also, do you mean oil or gasoline? (off topic - my car is happiest using Shell :-) – Rory Alsop Jul 11 '11 at 9:58
  • Related: skeptics.stackexchange.com/questions/3359/… – erekalper Jul 11 '11 at 14:16
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    here are some claims blog.gasbuddy.com/posts/… – GEdgar Nov 27 '15 at 18:25
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    It may not be a matter of the fuel but the fuel pump being inaccurate. – gnasher729 Nov 28 '15 at 10:22

According to The Gasoline Wars Chemical & Engineering News, vol. 87, pages 20-21, there are differences in the detergent content of gasolines. The 2009 article stated:

detergent levels dropped far enough earlier this decade that in 2004, automakers BMW, General Motors, Honda, and Toyota got together to create a standard for gasoline detergents called Top Tier. Marketers seeking to qualify their fuels as Top Tier Detergent Gasoline must pass tests for intake valve cleanliness, fuel injector fouling, and the like. Chevron and Shell are on the list, but other big brands like BP and Exxon are not.

The article explains that different brands vary in terms of the amount and chemical nature of the detergent additives.

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    BP and Exxon may not have been on the list in 2009, but they are now. See an updated list here. – tcrosley Dec 3 '15 at 6:24
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    I think it is reasonable to accept that different brands have different detergents and/or detergent concentrations. However, has anyone tested whether this has any significant effect on the engine or performance? – Oddthinking Dec 3 '15 at 11:27
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    @Oddthinking There are test results here: google.com/patents/US7901470 , but in terms of quantifying the deposits in the engine, not mileage directly. – DavePhD Dec 3 '15 at 13:18
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    @DavePhD: Unfortunately, patents aren't reliable sources of empirical data. – Oddthinking Dec 3 '15 at 15:04
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    @Oddthinking for the US patent application, at that time, the 6 inventors were required to state under oath and penalty of imprisonment and fines that they reviewed and understood the information in the application and that false statements could result in the imprisonment, fines and patent invalidity. So it's reliable to the extent that witnesses testifying under oath are reliable. Some of the other sources of skepticsSE answers don't even have one person stating under oath that they are true, let alone 6 people. – DavePhD Dec 3 '15 at 15:57

According to The analytical report on Consumer Gasoline Choices, conducted by Michael Stanley of Cleveland State University in 2015:

The major differences found in gasoline are the octane grade and the additives packages that gasoline retailers include in their fuel to create specific brands. Choosing the best gasoline for a vehicle first involves consulting the dealer or owner’s manual to determine w hat octane rating is appropriate for the vehicle. The second part of choosing the best gasoline involves using a brand of gas with higher levels of beneficial additives and detergents.


Choosing the right gasoline for a particular vehicle is one of the few options drivers have that can significantly improve or hinder the overall performance of their vehicle, as well as one of the most important choices for preventative maintenance. Continued use of low detergent fuel can cause lower fuel economy, loss of power, and fuel deposit buildup in engine parts with the potential for damage to the internal engine parts.

Consumers that want the best fuel should know the octane rating of their vehicle and always use that grade of fuel. To prevent harmful fuel deposit buildup, increase gas mileage, and boost engine power, consumers should use gas from a Top Tier gasoline retailer regularly to be sure the fuel they put in their gas tank meets minimum additive and detergent levels recommended by several automobile manufactures, and to maximize the benefits of clean burni ng efficient fuel.

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    Welcome to Skeptics! This "analytical report" was written by an undergraduate, and does not actually test any claims. Nor does it appear to cite any experiments that test any claims - it is largely repeating claims made by car manufacturers. The format makes it appear more authoritative than it actually is. – Oddthinking Dec 3 '15 at 11:23
  • Also, the idea that different octane grades have different performances/disadvantages doesn't appear to be within doubt - it is whether fuel with the same grade of octane across two brands has any difference. – Oddthinking Dec 3 '15 at 11:25
  • @Oddthinking, Fair enough. Will do some more digging. As you said, it seems far more authoritative than it actually is. – TheChetan Dec 3 '15 at 12:15

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