Is supermarket fuel lower quality than branded fuel?

No. All petrol sold in the UK must meet the BS EN 228 standard and all diesel must meet BS EN 590, regardless of where it is sold. Supermarket fuel comes from the same refineries and terminals as branded fuel; the main difference is the additive package blended in at the terminal.

Why do supermarkets sell fuel so cheaply?

Supermarkets use fuel as a footfall driver: a cheap forecourt attracts shoppers to the main store. They also run high-volume, low-margin operations and historically competed hard with each other on headline pump prices.

Will supermarket fuel damage my engine?

There is no evidence that fuel meeting the British standards damages engines. Standard supermarket petrol and diesel are legally required to meet the same minimum specifications as fuel from any other forecourt.

Is supermarket fuel always the cheapest option?

Usually, but not always. The CMA's 2023 road fuel market study found supermarket fuel margins had grown, and in some areas independent or branded forecourts can undercut the local supermarket. It is worth checking live prices rather than assuming.

Why Is Supermarket Fuel Cheaper?

Drive past a Tesco, Asda, Sainsbury's or Morrisons forecourt and the price on the totem is usually a few pence per litre below the branded station down the road. That gap has led to a persistent myth: that supermarket fuel must somehow be inferior. The short answer is that it isn't — it meets exactly the same legal standards — and the price difference comes down to business strategy, not quality.

Same standards, same refineries

All petrol sold in the UK must meet the British and European standard BS EN 228, and all diesel must meet BS EN 590. These standards set minimum requirements for octane or cetane rating, density, sulphur content and a long list of other properties. They apply to every forecourt in the country, whether the sign above it says Shell, BP, Esso or Asda.

In practice, supermarket fuel and branded fuel often start life in the same place. The UK's fuel supply chain runs through a relatively small number of refineries and import terminals, and retailers of all kinds draw from shared storage. What differs is the additive package — the detergent and performance additives blended in as tankers are filled. Branded retailers tend to promote their own proprietary additive blends, while supermarkets typically use a standard package. Both must still deliver fuel that meets the relevant British standard.

Fuel as a footfall driver

So why the lower price? Supermarkets treat fuel differently from oil company forecourts. For a supermarket, the petrol station is primarily a way to bring shoppers to the main store. A driver who fills up on the way in is more likely to do their weekly shop there too, so it can make commercial sense to run the forecourt on slim margins — the profit is made inside the store, not at the pump.

Supermarket forecourts are also very high-volume operations. Pumping far more litres than a typical independent station lets them spread fixed costs thinly and accept a smaller margin per litre. And because the big four supermarkets have historically watched each other's pump prices closely, competition between them has tended to keep headline prices down, which in turn pressures nearby branded stations. You can see this playing out in real time on our live fuel price map, where supermarket sites frequently anchor the cheapest prices in a town.

What the CMA found in 2023

It isn't quite the whole story, though. In 2023 the Competition and Markets Authority (CMA) published its road fuel market study, which found that supermarket fuel margins had grown in recent years — in other words, the traditional aggressive discounting had weakened, and drivers were paying more relative to wholesale costs than they had before. The study led directly to the government-backed Fuel Finder open data scheme, which requires large retailers to publish their pump prices — the same data that powers this site.

The practical takeaway is that "supermarket equals cheapest" is a useful rule of thumb, not a guarantee. In some areas an independent forecourt or a keenly priced branded site undercuts the local supermarket. Rather than assuming, it takes seconds to search stations near you and sort by price, or to compare prices by brand to see how the supermarkets stack up against each other and the oil majors this week.

Is there any catch to supermarket fuel?

For the vast majority of drivers in everyday cars, no. Fuel that meets BS EN 228 or BS EN 590 will run your engine as the manufacturer intended, and there is no credible evidence that standard supermarket fuel causes harm. Millions of tanks are sold every week without issue.

There are a couple of honest caveats. If you drive a high-performance car that specifically requires higher-octane super unleaded, you should use it wherever you buy fuel — some supermarket sites carry super unleaded and premium diesel, but not all do. And if you value a particular branded additive package, that is a legitimate preference; just be aware you are paying for the additives and the brand, not for a different base fuel. We look at whether that premium is worth it in our guide to premium fuels.

How to make sure you're actually getting the best price

Because retailers now publish price changes through the Fuel Finder scheme, you no longer need to guess. Check current prices before you leave, keep an eye on recent price drops in your area, and if you time your fill-ups flexibly, see our analysis of the best day to buy fuel. A few pence per litre may not sound like much, but across a year of motoring the savings from consistently choosing the cheaper forecourt add up — wherever the fuel happens to come from.