Put E10 in a car that isn't approved? What to do

Accidentally filled a non-approved car or bike with E10? What happens, whether you need to drain the tank, and how this differs from putting petrol in a diesel.

Updated 25 October 2026

Don't panic: this is not like diesel in a petrol car

Putting E10 in a petrol vehicle that isn't approved for it is not a misfuel emergency. The UK government's advice is that a single tank will not cause damage: simply fill up with E5 next time. You do not need to have the tank drained.

Different problem: if you put petrol in a diesel (or diesel in a petrol car), do not start the engine. Call your breakdown service.

What to do

Drive normally and use the fuel.
Next time, fill with E5 super unleaded and keep using it.
If the vehicle will now be stored for a long time, top it up with E5 first so the E10 is diluted.
If you notice fuel smells, leaks or rough running in an old or classic vehicle, have the fuel lines and seals checked.

Why repeated use is the real risk

Ethanol is a solvent and holds water. Over months, it can degrade some older rubber hoses, seals and gaskets, some fibreglass tanks and carburettor parts, and corrode some metals. That is why manufacturers tell owners of excluded models to keep using E5.

Check your car in 10 seconds

Pick your make and year for the manufacturer's E10 answer.

Open the checker

Frequently asked questions

Do I need to drain the tank after one fill of E10?

No. UK government advice is that one tank is fine; fill with E5 next time.

Will one tank of E10 void my warranty?

It is very unlikely to matter, but if in doubt ask your dealer and keep using the fuel your handbook specifies.

My car is a classic. Is it different?

Classic cars are more sensitive. One tank is still unlikely to cause damage, but switch back to E5 and see our classic car guide.

Sources

GOV.UK – E10 petrol explained (checked 25 October 2026)

Related guides

General information only. Always follow your vehicle handbook and the manufacturer's advice.