Is it always serious if I've put the wrong fuel in?

It depends on whether the engine was started and how far it ran. If caught before starting, it's usually just an inconvenience needing a drain; if driven for a while, damage risk increases.

Can I just add the correct fuel on top?

No — this doesn't fix contamination and can make the mixture worse. The tank generally needs draining properly.

Will my breakdown cover pay for this?

Some policies include misfuelling assistance, others don't. Check your policy or ask the recovery firm what's typically needed if you don't have cover for it.

Put the Wrong Fuel In? What to Do Next

Do not start the engine

If you realise before starting the car, don't turn the key. The single biggest cause of expensive damage in misfuelling cases is running the wrong fuel through the system, which circulates it into the fuel lines, injectors and sometimes the engine itself.

If you've already driven off

If the engine has run and you notice problems — rough running, loss of power, knocking noises, warning lights — pull over safely as soon as you can and switch off. The earlier you stop, the less contaminated fuel gets circulated.

Don't try to drain it yourself at the roadside

This isn't a job to improvise. Fuel system draining needs the right equipment and is usually done by a specialist or garage, not attempted with a fuel can and hope at the side of the road.

Call for recovery, not a tow to a fuel station

The car needs to go to a garage or specialist for the tank to be drained and the system flushed if necessary, not simply topped up with the correct fuel — mixed fuel left in the tank can still cause problems.

Tell the recovery driver what happened

Being upfront helps them recommend the right destination — some garages specialise in fuel contamination and can drain the tank on-site or arrange it quickly, which can save you a second trip.

Check whether it's covered by insurance

Some comprehensive policies, and some specific misfuelling add-ons or breakdown cover extras, include cover for this. It's worth checking before you pay out of pocket, though many standard policies don't cover it automatically.

Frequently asked questions

Is it always serious if I've put the wrong fuel in?: It depends on whether the engine was started and how far it ran. If caught before starting, it's usually just an inconvenience needing a drain; if driven for a while, damage risk increases.
Can I just add the correct fuel on top?: No — this doesn't fix contamination and can make the mixture worse. The tank generally needs draining properly.
Will my breakdown cover pay for this?: Some policies include misfuelling assistance, others don't. Check your policy or ask the recovery firm what's typically needed if you don't have cover for it.

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What to do if you put the wrong fuel in your car