It is one of the most persistent myths in motoring. Pull into a Tesco or Asda forecourt and someone will tell you that supermarket fuel is lower quality, dirtier, or worse for your engine than branded fuel from BP, Shell or Esso. But is any of it true?
The short answer is no. Supermarket petrol is not bad for your car.
All petrol starts in the same place
Every litre of petrol sold in the UK, regardless of where you buy it, comes from the same refineries. Tesco does not have its own refinery. Neither does Asda or Morrisons. All fuel is refined to the same British and European standards (BS EN 228 for petrol, BS EN 590 for diesel) before it goes anywhere near a forecourt.
Fuel is transported through a shared pipeline network to regional depots. At this point, different companies add their own additive packages before delivery to forecourts. This is where the difference between branded and supermarket fuel actually exists, and it is much smaller than most people think.
What about additives?
Branded fuels like Shell V-Power or BP Ultimate contain higher concentrations of cleaning additives designed to reduce engine deposits and improve performance. These are genuinely useful, particularly for older engines or vehicles that are driven mainly on short journeys where deposits can build up more quickly.
Supermarket fuel meets the minimum additive requirements set by UK law but typically does not contain the same concentration of premium cleaning additives as branded fuels. This does not make it harmful. It just means it is standard rather than premium.
If you drive a modern car and get it serviced regularly, you are unlikely to notice any difference between supermarket and branded fuel in normal use. If you drive an older high-performance engine or do a lot of short journeys, premium branded fuel may offer a marginal benefit over time.
The price difference
Based on current live prices across UK forecourts, branded station fuel typically costs 5p to 15p per litre more than supermarket fuel. On a 50 litre fill that is between £2.50 and £7.50 extra every time you fill up. For most drivers, the marginal benefit of premium additives does not justify that cost.
What the manufacturers say
Major car manufacturers design and test their engines to run on fuel meeting the minimum UK and European standards. Using supermarket fuel that meets those standards will not void your warranty or damage your engine. The idea that manufacturers secretly recommend avoiding supermarket fuel is simply not true.
The verdict
Supermarket petrol is not bad for your car. It meets the same legal standards as branded fuel, comes from the same refineries, and will not damage your engine. Branded fuels offer a genuine but modest benefit through higher additive concentrations, which may be worth paying for if you have an older or high-performance engine. For the majority of drivers with modern cars, filling up at Tesco or Morrisons is a perfectly sensible choice that will save you money with no meaningful downside.
Fuel prices referenced in this article are based on live data from the UK Government FuelFinder service, updated hourly.