Mythbust supermarket petrol for me, please.
August 30, 2009 12:18 PM   Subscribe

Is supermarket petrol bad for my car?

It seems to be common knowledge that supermarket petrol from Tesco, Asda or what have you stations is inferior to the stuff from a "proper" petrol station. That it damages the engine in the long run for any of a variety of vague and poorly explained reasons.

Is there any substance to this idea, or is it just superstition? Googling gave me lots of conjecture but nothing authoritative.

UK-centric in case it matters. Thanks.
posted by Lorc to Shopping (12 answers total) 1 user marked this as a favorite
Unless you're purchasing something like Shell Optimax (i.e. fuel with additives), it's identical.
Use away.
posted by knapah at 12:23 PM on August 30, 2009

It's cheap because they're using it as a loss leader to get people into their stores.
posted by knapah at 12:32 PM on August 30, 2009

Best answer: From What Car?

Q: Is it true that the fuel sold at supermarket petrol stations is not of the same quality as that as you would buy from a dedicated petrol station?
Alex Wells

A: According to the Petrol Retailers Association, there is no difference between the standard petrol you buy from supermarkets or franchised petrol stations. In most cases the petrol and diesel is even produced at the same refinery and delivered in the same trucks.

The exception to this is specialist fuels, such as Shell’s Optimax and BP’s Ultimate. In their case, the fuel is enhanced with additives, which produce that brand’s particular properties.

posted by knapah at 12:32 PM on August 30, 2009 [2 favorites]

Supermarket pertrol is the same as anywhere else, short of the 'supreme psuedoscience version!' stuff you can choose to pay lots extra for at branded petrol stations. The reason it's so cheap is that it is a loss leader that gets people onto the supermarket forecourts, and then into the supermarket itself.
posted by Dysk at 12:32 PM on August 30, 2009

In the US, it is from the same as gas station gasoline.
posted by tamitang at 12:39 PM on August 30, 2009

hmmmm. should have said "same refineries and is the same"
posted by tamitang at 12:40 PM on August 30, 2009

Almost certainly exactly the same, given the global nature of fuel companies.
posted by knapah at 1:25 PM on August 30, 2009

Probably not exactly, if only for the simple reason that we don't have many independent petrol stations. So anything beyond the first paragraph of odinsdream's post doesn't apply.

It is still almost certainly the case that there are very, very few sources of petrol, and that they are used interchangeably by most or all of the big players (i.e. branded petrol stations and supermarkets) as they are identical product.
posted by Dysk at 1:34 PM on August 30, 2009

For the most part, all fuel is going to be the same. The only time that you encounter a difference is the result of one gas station being busier than another. A busy gas station tends to have fresher gas since they run out faster and are refreshed more often. A station that sees less business has an increasing likelihood of having stale fuel.
Aside from that, the pump will have a sticker that indicates the percentage of ethanol added, if it makes a difference to you.
posted by Jon-o at 1:41 PM on August 30, 2009

Jon-o, read the OP's post properly.

There are no stickers indicating percentage of ethanol added on the pumps in the UK.
posted by Dysk at 1:56 PM on August 30, 2009

I have gotten the impression that, in days of yore, there might have been differences in terms of how gas stations stored the fuel or maintained their tanks, so gas from Joe's Poorly-Run Station might have small amounts of suspended grit or emulsified water or dissolved crud. I don't think this has been a concern since, like, the 1950s or something, but it persists as a cultural memory, perhaps helped along by the occasional bits of FUD from marketing departments.
posted by hattifattener at 4:09 PM on August 30, 2009

hattifattener, part of it is probably also to do with improvements in engine tech - carburettors are much more prone to problems from impurities in fuel than are the modern filters that sit before direct-injection systems.
posted by Dysk at 4:29 PM on August 30, 2009

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