Fuel Types & Quality E5 vs E10

What is the difference between E5 and E10 petrol?

Q: What is the difference between E5 and E10 petrol?

E10 contains up to 10% ethanol and E5 contains up to 5%. E10 has been the standard 95-octane unleaded grade at UK pumps since September 2021. E5 is still sold as a higher-octane super unleaded grade for vehicles that are not compatible with E10, such as some older cars and classics.

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E5 and E10 petrol differ in how much ethanol they contain — E5 has up to 5% ethanol, while E10 has up to 10%. E10 became the standard grade of unleaded petrol at UK pumps in September 2021, replacing E5, which is now only available as a higher-octane protected grade for vehicles that cannot use E10.

What the Numbers Mean

Ethanol content: The number after the E refers to the percentage of ethanol blended into the petrol. E10 contains up to 10% ethanol; E5 contains up to 5%. 2

Why ethanol is added: Ethanol is a renewable fuel made from plant material. Blending it into petrol reduces net CO2 emissions because the plants absorbed carbon as they grew. 2

Same base fuel, different blend: Both grades use the same refined petrol base. The only structural difference is the proportion of ethanol mixed in before it reaches the pump. 3

How E10 Became the UK Standard

Introduced in September 2021: The UK government mandated E10 as the standard 95-octane unleaded grade from September 2021 to help reduce transport carbon emissions. 2

Environmental benefit: Switching the UK to E10 is estimated to be equivalent to taking around 350,000 cars off the road each year in terms of CO2 reduction. 2

E5 retained as a protected grade: E5 is still sold at most UK forecourts as the higher-octane (97+) super unleaded grade — for example, Shell V-Power or BP Ultimate — specifically to protect owners of older vehicles. 5

Compatibility and Fuel Economy

Most modern cars are fine: Around 95% of petrol cars currently on UK roads are compatible with E10. You can check your specific vehicle on the government's E10 compatibility checker. 2

Older vehicles may be affected: Some vehicles made before 2002, plus certain classics, motorcycles, and small engines, may have rubber seals or metal components that ethanol can degrade over time. 4

Slight MPG reduction with E10: Ethanol contains less energy per litre than petrol, so E10 can reduce fuel economy by around 1–2% compared with E5. For most drivers this is negligible. 5

Which Grade Should You Use?

Use E10 if your car is compatible: If your vehicle is on the government's compatible list, E10 is perfectly safe and is the cheapest option at the pump. 2

Stick to E5 super unleaded if in doubt: If your car is older or you are unsure, use the E5 super unleaded grade as a precaution until you have confirmed compatibility. 4

Compare prices before you fill up: Super unleaded E5 typically costs 10–15p per litre more than standard E10. CheckFuelPrices shows live prices for both grades at thousands of UK stations so you can find the best deal nearby. 1