E10 vs E5 petrol: which goes in your car?
10 July 2026·5 min read
What E10 and E5 actually are
E10 has up to 10% bioethanol, E5 up to 5%. Since September 2021, E10 has been the standard grade on UK forecourts. E5 now lives mainly as super unleaded, usually a bit more expensive than E10.
You can compare live prices for both grades by town or postcode on the fuel finder, without driving between pumps.
Starting with compatibility
Every petrol car sold new in the UK since 2011 runs on E10, and most European petrol cars from the early 2000s do too. For anything older or where you are unsure, the Government's official E10 checker is the right place to look. If it cannot confirm your car, use E5.
What E10 does to economy
Ethanol holds less energy per litre than petrol, so E10 returns about 1 to 2% less than E5 in a car made for it. On a typical 40 mpg car that is a couple of miles per gallon each tank. Small per fill, real over a year.
Classic cars and cars that sit
Ethanol absorbs water, so E10 does not keep as well and can soften old seals, rubber lines and carburettor parts over time. If the car sits a lot or is a classic, either use E5 or keep the tank fairly full. Fresher fuel and less air in the tank means less moisture.