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What is the difference between the cheapest fuels in a place like Tesco's and the 'high quality', highly priced competitors? Is there actually any noticeable difference in available power, engine smoothness, efficiency, maintenance costs etc?

Personally I've always used the cheapest I can just because I don't know what the difference is that I would be paying for!

Can anyone justify their use of an expensive fuel having had a bad experience with a cheap fuel in their car in the past?

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    It would be helpful to know what kind of vehicle you drive.
    – race fever
    Jan 4, 2016 at 2:36
  • I drive a VW Passat B5 2004 (petrol) Jan 4, 2016 at 7:17
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    This question and the commentary associated with it are edging very close to opinion-based and / or shopping advice. I'm not seeing enough hard data to make it sound like this question is answerable as written. More specificity is required, at a minimum.
    – Bob Cross
    Jan 4, 2016 at 15:10
  • Does the existence of the Top Tier organization, which rates fuel quality, matter here? Is there a similar organization in the UK or Europe in general?
    – kmarsh
    Jan 4, 2016 at 16:16

4 Answers 4

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Gasoline is made in large batches. Each batch has a number of attributes that should be met; Octane, specific chemistry, volatility, contaminates, ethanol content, and others. The output is dependent on the crude that went into the refinery and the processes the refiner has at hand to process it. Refineries vary in there capabilities.

There are over 60 different fuel variations required by government regulation in the US. These are formulated to help with air pollution concerns that vary by region, mostly, but not always due to average weather conditions. Regulators require an average quality across many batches. So that means there are batches that do not meet standard. These are often purchased by low price marketers who then pass on the "savings". Batches are often in the 2 million liter range. Also the brand specific detergent additives are put in at the truck level only in those loads headed for specific retail stations. These additives are expensive and usually not used in the thrift-ed brands.

So yes, there are many differences and the answer is, as is often the case, It Depends!

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As far as I understand it, the 'premium' brands will have the fuel mixed to their own specifications, which may include particular detergents, additives etc. The cheaper brands will simply buy whatever is cheapest - so the Tesco one could be identical to Shell one week (if Shell happened to have a surplus), BP the next, a mixture of things the week after, and so on. As Fed Wilson says, often they will by the stuff that didn't make the grade for the premium suppliers.

So as Fred says, 'it depends' - but the premium fuel will be more consistent, generally.

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  • Thats a fair point. So effectively the cheaper fuels could be fine half the time but due to their lack of consistency you are taking more of a risk by using them. Jan 4, 2016 at 10:24
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    Yep - as some people found to their cost a few years ago when Tesco got a contaminated batch and loads of cars needed their fuel systems cleaning out
    – Nick C
    Jan 4, 2016 at 10:25
  • I didn't know that! Good to know. Jan 4, 2016 at 10:26
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Depends on your vehicle. Most are tuned to use regular fuel, which hovers around the 87 octane rating. If your vehicle is turbo or supercharger then it should use a higher octane rating. Refer to the user's manual.

Real difference? None. Some sell fuel with additives that "help" with keeping your fuel system "clean". But I have never seen any difference.

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    "None" is not the case. Please see the other answers. You may not have noticed a difference, but even the detergents used in different brands have different characteristics.
    – Rory Alsop
    Jan 4, 2016 at 12:13
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    @RoryAlsop Sure, but the detergents are commonly the same type of additive with a different name for marketing purposes. Only when you move into higher octane fuel (off road race fuel) will you see differences from brand to brand and even batches. But the regular consumer grade is virtually the same across the board due to regulations. Should the OP worry about it? Not with his VW. Won't make a difference.
    – race fever
    Jan 4, 2016 at 13:15
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    Actual differences the OP should notice between a no-name fuel with no additives, and a named fuel with detergents etc include longer lifespan for the engine, longer time between cat replacements, possibly smoother starting on cold mornings and various others. Even in his normally aspirated VW.
    – Rory Alsop
    Jan 4, 2016 at 13:21
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    If you want to make an assumption that you will mix fuels over time, that changes the question. I know that I only use one type of fuel. The same type every time. I'm sure others do the same.
    – Rory Alsop
    Jan 4, 2016 at 14:31
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    In those cases I'd have to agree with you. I know I do have control, as my provider is very specific (which is why I use them, as my engine has some specific requirements)
    – Rory Alsop
    Jan 4, 2016 at 15:03
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In the United States, if you are buying a listed Top Tier gasoline, all other quality differences (within grade) are inconsequential.

I have to note, it is possible that gasoline not listed as Top Tier could be high quality.

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    That sounds like a good system as the customer then knows that any "Top Tier" marked fuel should be a trustworthy fuel to use in their car Jan 4, 2016 at 14:33

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