E10 or super unleaded (E5)? Which petrol should you buy?
E10 has been standard unleaded since 2021. When super unleaded E5 is worth paying extra for, which cars should avoid E10 and how to check yours.
Since September 2021 the standard unleaded petrol in the UK is E10, which contains up to 10% bioethanol. The previous standard, E5 (up to 5% ethanol), is still sold as super unleaded, usually at 97–99 octane (RON).
Does your car need E5?
Almost all petrol cars built since 2011 are compatible with E10. Some older cars, classic cars, many mopeds and some motorcycles are not. Check your registration on the GOV.UK vehicle checker before you buy.
Is super unleaded worth the extra?
Super unleaded usually costs 10–15p a litre more. Unless your manufacturer specifies high octane (some performance cars do) or your vehicle is not E10-compatible, you are unlikely to save money. Ethanol holds slightly less energy than petrol, so E10 can return marginally fewer miles per gallon, but the difference is normally small and far less than the price gap.
Compare prices
See the live average for unleaded E10 and super unleaded, or check the cheapest stations.
What the labels mean
E10 is petrol that contains up to 10% bioethanol; E5 contains up to 5%. Since September 2021 E10 has been the standard unleaded grade at UK forecourts, and E5 is still sold as “super unleaded” (usually 97 octane or higher). Both are legal for road use, and the pump label tells you which one you are choosing.
Which one should your car use?
Most petrol cars built since 2011 are E10-compatible, and the large majority of earlier cars from 2000 onwards can also use it. Some older cars, classic cars and a few motorcycles and mopeds are not compatible. The Government provides a registration-number checker, linked below, and your handbook or fuel-filler flap usually states the answer too. If your car is not compatible, E5 (super unleaded) is the correct fuel.
Is super unleaded worth the extra money?
Super unleaded costs more per litre – often by a noticeable margin. To pay off, it would need to improve your fuel economy by roughly the same percentage that it costs more. For example, if super costs 10p more on a base of 170p, that is about 6% more per litre, so the car would need to go about 6% further on a litre to break even. Independent tests of ordinary cars have usually found smaller gains than that, so for most drivers the standard grade is cheaper per mile. Cars whose manufacturer specifies a higher octane rating are the exception, because using a lower grade can reduce performance or require the engine to adjust.
Does E10 use more fuel?
Ethanol contains less energy than petrol, so E10 gives slightly lower mileage than E5 – in the order of one or two percent. In practice the difference is hard to notice from tank to tank, because driving style, weather and traffic have a larger effect. If E10 is also cheaper per litre than E5 by more than that, it works out cheaper per mile.
Where to check prices
Our E10 page and super unleaded page show the current average and the cheapest stations for each grade.
Frequently asked questions
Can I put E10 in any petrol car?
Most cars made since 2011 can. Older and classic cars may not – use the GOV.UK checker with your registration number.
What if I put E10 in a car that needs E5?
One tank is unlikely to cause immediate damage, but fill up with E5 next time and keep using it. Repeated use of E10 in an incompatible engine can damage seals and fuel-system parts.
Can I mix E10 and E5 in the same tank?
Yes, if your car can use E10. Mixing the two simply gives a blend with a ethanol content between 5% and 10%.
What happens if I put E10 in a car that cannot use it?
A single tank is unlikely to cause damage, but ethanol can degrade some older rubber and metal components over time. Fill up with E5 next time and check your handbook.