Why supermarket fuel is usually cheapest
Walk into any Tesco or Asda and you'll likely find petrol 4–6p cheaper than the BP or Shell across the road. This isn't a coincidence or a temporary promotion. It's the result of a deliberate business strategy that's been running for decades, and understanding it helps you make better decisions about where to fill up.
The loss-leader business model
Supermarkets treat forecourt fuel as a footfall driver, a product sold at a thin margin specifically to attract customers who then spend money in-store. Tesco, Asda, Sainsbury's and Morrisons all operate on this principle. The average customer who stops to fill up also goes inside and spends £30–50 on groceries. The economics work even if the fuel itself barely breaks even.
Branded forecourts (BP, Shell, Esso, Texaco) operate a fundamentally different model. Their margin per litre is higher because fuel is their primary product, not a supporting one. They also carry the cost of branding, loyalty programmes, and in many cases premium facilities.
Buying power and bulk contracts
The major supermarkets buy fuel in enormous volumes and negotiate supply contracts that smaller operators cannot access. Tesco alone runs hundreds of forecourts. This scale gives them leverage with wholesale fuel suppliers that an independent station of equivalent size simply doesn't have. Combined with their efficient supply chains (many share distribution networks with their food logistics operations), and their delivered cost per litre is genuinely lower.
How the prices compare by brand
The price gap between brands is consistent across the UK. Based on national average data from PumpItDown's station database, supermarket forecourts typically sit 4–6p below the major branded networks. Motorway services sit in a league of their own.
When supermarket fuel isn't worth the trip
The maths only works if the supermarket is on your route or very close. Driving 3 miles out of your way to save 7p per litre on a 40-litre tank saves £2.80 but burns additional fuel worth roughly £1.50. The net saving is about £1.30. That may not be worth the extra time and mileage. The sweet spot is a supermarket forecourt that's already on your commute or close to a regular shopping run.
Check prices near you before leaving home. A supermarket 0.5 miles away that's 7p cheaper is a clear win. One that's 5 miles in the wrong direction may not be worth it.
Loyalty vouchers and promotional discounts
On top of everyday lower prices, supermarkets periodically run fuel discount promotions tied to in-store spending. The most common format: spend £40 or £50 in store and receive a voucher for 10p off per litre at the forecourt. These promotions appear at Tesco, Sainsbury's and Morrisons at various points through the year, typically around high-footfall periods such as Christmas, summer school holidays, and Easter.
When active, these vouchers can extend the price gap between supermarket fuel and the cheapest branded forecourt to 14–18p per litre or more. On a 60-litre fill, a 10p voucher represents a saving of £6 on a single transaction. The offers are typically accessible through the Tesco, Sainsbury's and Morrisons smartphone apps, or printed on till receipts. They expire within two to three weeks, so they are worth using promptly.
The practical implication: if you already shop regularly at a major supermarket, the combination of everyday lower prices, loyalty points accumulation, and occasional voucher promotions means supermarket fuel can effectively cost 15–20p per litre less than branded alternatives across the year. The full advantage is larger than the advertised pump price difference suggests when all elements are combined.
Is supermarket fuel lower quality?
This is a common concern and the short answer is: no. All fuel sold at UK forecourts must meet the same EN228 standard for petrol and EN590 for diesel. Supermarket fuel meets exactly the same specification as BP or Shell. The difference is that branded fuels often include additional proprietary additive packages: Shell's V-Power, for instance, includes deposit-cleaning compounds. For most standard engines doing normal driving, these additives make no meaningful difference. For high-performance engines or cars with known injector deposit issues, there may be a marginal benefit to premium branded fuel.