E10 vs E5: which petrol should you buy?
Published - 4 min read
What E10 and E5 petrol are, whether your car can use E10, and when super unleaded (E5) is worth paying extra for.
The short answer
If your petrol car is compatible with E10 - and most are - standard unleaded (E10) is the sensible everyday choice. It is the standard, lower-priced petrol grade at UK forecourts. Super unleaded (E5) is mainly worth buying if your vehicle isn't E10-compatible, or its handbook asks for a higher-octane fuel.
What the names mean
- E10 is petrol blended with up to 10% renewable ethanol. It became the standard unleaded grade in Great Britain in September 2021, and has since become the standard in Northern Ireland too.
- E5 is petrol with up to 5% ethanol. At most forecourts it is now sold as super (or premium) unleaded, which usually also has a higher octane rating.
The number is the maximum ethanol content, not the exact amount in every litre.
Can my car use E10?
According to the government, the vast majority of petrol cars on UK roads can use E10, and all petrol cars built since 2011 are compatible. Some older vehicles are not - particularly classic cars and some older motorcycles and mopeds.
The easiest way to check is the official GOV.UK E10 vehicle checker. Your handbook or the manufacturer can also tell you.
What if I put E10 in a car that isn't compatible?
GOV.UK's guidance is that filling up with E10 by mistake in a vehicle that isn't compatible shouldn't cause harm as a one-off, as long as you fill up with E5 next time. Using it repeatedly is a different matter: over time, ethanol can damage seals, plastics and metals in fuel systems that weren't designed for it.
Does E10 cost more per mile?
Ethanol contains a little less energy than petrol, so some drivers see slightly fewer miles per gallon on E10. For most cars the difference is small. To compare fairly for your own car, work out your real cost per mile on each fuel (our MPG guide shows how) using the prices at stations near you.
You can see today's national average for both grades, and the gap between them, on the UK Fuel Price Index.
When super unleaded (E5) makes sense
- Your vehicle isn't E10-compatible.
- Your handbook specifies a higher octane rating, such as 97 or 98 RON, as some performance cars do.
- You own a classic or rarely used vehicle. Ethanol-blended petrol is more prone to absorbing moisture when it sits in a tank for long periods, so many owners of these vehicles prefer E5.
If your car is designed to run on standard 95 RON unleaded, a higher-octane fuel is unlikely to make a noticeable difference to economy or performance. The handbook is the best guide to what your engine needs.