What is E10 fuel, and should you be worried?
In September 2021, the UK switched standard petrol from E5 (5% ethanol) to E10 (10% ethanol). For the vast majority of drivers it was a non-event. For a small number of older or specialist vehicles, it matters. Here's exactly what changed, who it affects, and what you should do about it.
Why ethanol is added to petrol
Ethanol is a biofuel produced from crops like wheat and sugar beet. Blending it into petrol reduces the proportion of fossil fuel per litre, which lowers the carbon intensity of the fuel. The UK government introduced the E10 switch as part of its carbon reduction commitments. It's estimated to reduce CO₂ emissions equivalent to taking 350,000 cars off the road each year.
Ethanol has a lower energy density than petrol. A litre of ethanol contains roughly 34% less energy than a litre of pure petrol. Blended at 10%, this reduces the energy content of E10 by about 2.3% compared to E5, meaning a very marginal reduction in your fuel range.
Is your car compatible?
The Government's E10 compatibility checker covers most cars. As a rule of thumb: virtually all petrol cars manufactured from 2011 onwards are E10 compatible. Most cars made from 2000 onwards are fine. Cars that may not be compatible include:
- Classic and vintage cars: rubber seals, hoses and certain metals used in older fuel systems can degrade with higher ethanol content.
- Some motorcycles and mopeds: particularly older models. Check your manufacturer's guidance.
- Small engines: lawnmowers, outboards and some garden machinery. Ethanol absorbs water, which can damage carburetors in equipment that sits unused between seasons.
- Some performance/specialist vehicles: a small number of high-performance models from the early 2000s were built before E10 compatibility was standardised.
The Government's E10 checker at check-your-vehicle.service.gov.uk lets you enter your registration number to confirm compatibility.
If your car isn't compatible
E5 "super" petrol (97+ RON) remains available at all UK forecourts and is guaranteed to do so until at least 2026. If your vehicle isn't E10 compatible, you should use super unleaded (E5) as your standard fuel. Yes, it costs 10–15p more per litre, but it's the right fuel for your car.
Using E10 in an incompatible vehicle won't cause immediate catastrophic failure. Filling up with the wrong fuel once isn't a crisis. Long-term regular use, however, can degrade fuel lines, seals and other rubber components. If you're not sure, check.
If your car was made after 2011, you've been running on E10 for over three years and may not have noticed. The ~2% range difference is barely perceptible in real-world driving. Don't switch to super unleaded unnecessarily. It costs 10–15p more per litre.