Guide
Why supermarket fuel is cheaper
Supermarkets sell fuel at a wafer thin margin to get you through the doors. Usually that makes them the cheapest forecourt in town, but not always, and the exceptions are worth knowing.
If you have noticed that the supermarket forecourt almost always undercuts the branded station down the road, you are not imagining it. Supermarkets price fuel differently from oil companies, on purpose, and the reason says a lot about how to find the cheapest tank near you.
Fuel as bait
To a supermarket, the forecourt is not really a fuel business. It is a way to pull you into the car park and, ideally, through the doors to do a shop. Cheap fuel is bait, sold at a wafer thin margin, sometimes at little more than cost, because the profit the chain is chasing is in the trolley, not the tank. An oil branded station has no aisles of groceries to fall back on, so it has to earn its living on the fuel itself and prices accordingly.
Add the sheer volume a big supermarket forecourt shifts, and its buying power, and you get a station that can consistently sit a few pence under the branded competition without losing money overall.
How big is the gap?
Against a nearby branded station, supermarkets typically come in around three to six pence a litre cheaper, though it varies by area and by week. Against a motorway services the gap is far wider, often fifteen to twenty pence a litre, which is why filling up on the motorway is the single most expensive way to buy fuel in Britain. On a 55 litre tank, six pence a litre is a little over three pounds, and twenty pence is more than a tenner, every single fill.
When the supermarket is not the cheapest
Usually is not always, and it pays to know the exceptions.
Areas with no competition. The supermarket discount is really a competition discount. Where a town has one supermarket and no rival forecourt nearby, that station has little reason to keep its price keen, and a busier location elsewhere can beat it. The pattern is local, not national.
Members clubs. Warehouse clubs such as Costco are often cheaper than the supermarkets, sometimes by a wide margin, but you need a paid membership to use the pumps, so they only pay off if you fill up often or shop there anyway.
The odd independent. Some independents, particularly near fuel terminals or on fiercely contested roads, quietly match or beat the supermarkets. They are the exception, but they exist, and only a look at every forecourt will find them.
Is supermarket fuel lower quality?
This is the worry that keeps some drivers paying more, and it is largely a myth. The petrol and diesel sold on a supermarket forecourt meet the same British standards as any other, and much of it comes from the very same terminals as the branded fuel. The real difference is in the additive packages that premium fuels carry, and for an ordinary car those make little difference worth the money. If you want the detail on grades and when a premium fuel is actually worth it, see our guide to E10 versus E5 petrol.
The only way to be sure near you
Because the cheapest forecourt is a local question that changes street by street, the honest answer is to look rather than assume. Put your postcode into the price finder and it ranks every forecourt within five miles by price, supermarkets and independents and branded stations alike, updated twice a day from official data. That is how you catch the weeks when the supermarket is not, in fact, the cheapest game in town.
Common questions
Why is supermarket fuel cheaper than branded stations?
Supermarkets treat fuel as bait to pull shoppers into the store, so they sell it at a very thin margin, sometimes near cost, because they make their money in the store rather than on the tank. Their volume and buying power let them sit a few pence under branded stations without losing out overall.
How much cheaper is supermarket fuel?
Against a nearby branded station, supermarkets are typically around three to six pence a litre cheaper, varying by area and week. Against motorway services the gap is far larger, often fifteen to twenty pence a litre, which makes the motorway the most expensive place to fill up.
Is supermarket fuel lower quality?
No. Supermarket petrol and diesel meet the same British standards as branded fuel and often come from the same terminals. The difference is in the additive packages of premium fuels, which make little difference worth paying for in an ordinary car.
Is the supermarket always the cheapest place to buy fuel?
Not always. In areas with little competition a lone supermarket has less reason to keep prices low, members clubs such as Costco can be cheaper for those who pay to join, and the odd independent beats them. Checking every forecourt near you is the only way to be sure.