Fuel
E10 vs E5 Petrol: Which Should You Use?
Since September 2021, E10 has been the standard grade of unleaded petrol at UK forecourts. It replaced the old E5 standard to meet renewable fuel targets. For most drivers, the change is invisible. For owners of older vehicles, it matters a great deal.
1. What do E5 and E10 actually mean?
The number refers to the percentage of bioethanol blended into the petrol. E5 contains up to 5% ethanol; E10 contains up to 10%. The rest is standard petrol. Ethanol is a renewable fuel derived from plant material (wheat, sugar beet). It burns cleaner than fossil fuel, which is why E10 reduces CO2 emissions by roughly 2% compared with E5.
2. Is E10 safe for my car?
All petrol cars manufactured from around 2011 onwards are E10 compatible — check your owner's manual or the sticker inside the fuel filler cap. Most cars from 2000–2011 are also fine. The vehicles at risk are pre-2000 classics, some motorcycles, and certain models from the early 2000s. The DVSA's E10 compatibility checker (gov.uk) lets you check any UK-registered vehicle by make and model. The problem is that ethanol is more corrosive than petrol and can degrade older rubber seals, fuel hoses, and carburettor components.
3. What happens if you put E10 in an incompatible car?
One or two accidental fill-ups will not destroy your engine — the damage is cumulative. The ethanol absorbs water from the atmosphere, which can cause fuel system corrosion over time. Rubber seals can swell and crack. You may notice rough running, poor starting, or a higher fuel consumption. If you realise you have filled up with E10 in an incompatible vehicle, top up with E5 as soon as possible to dilute it.
4. Where to find E5 petrol in the UK
E5 is still legally available at UK forecourts — it is sold as 'Super Unleaded' (97+ octane). It costs significantly more than E10 standard unleaded, typically 10p–20p more per litre. Major supermarkets stock it, as do most large branded forecourts. If you drive a classic or incompatible vehicle, the extra cost is unavoidable. Use Kermo's fuel price tool to find the cheapest E5 (Super Unleaded) near you.
5. Does E10 affect fuel economy?
Yes, slightly. Ethanol has a lower energy density than petrol, so E10 delivers marginally fewer miles per litre compared with E5. In real-world driving, the difference is typically 1–3% worse fuel economy. For most drivers, the lower pump price of E10 more than compensates for this. If you are driving a compatible modern car, there is no reason to pay for E5.
Find the cheapest Super Unleaded (E5) near you
Use Kermo to turn the information in this guide into a practical vehicle or fuel check.
Find the cheapest Super Unleaded (E5) near you