What's misfuelling? What should I do if I fill up with the wrong fuel?

3 minutes

Misfuel? What’s that?

Putting the wrong type of fuel in your car is known as misfuelling. You’ll be forgiven for thinking it’ll never happen to you but, trust us, it can happen to anyone! In fact, it’s estimated around 150,000 drivers misfuel in the UK every year. 

There's no need to panic though. We’re here to let you know what to do if you end up with petrol in a diesel car or diesel in a petrol car.

Steps to take when you’ve misfuelled

  • Don’t start your car. If you’ve already driven off before realising the mistake, stop somewhere safe.
  • Call your breakdown or insurance provider. Your policy may cover misfuelling so get in touch and follow their instruction.
  • If you have breakdown cover, they can come out and drain your fuel tank.

What happens if I fill up with petrol instead of diesel?

It’s more common for petrol to be put into a diesel car, the petrol nozzle is smaller and will fit into the diesel tank. This can be a serious problem as diesel cars use the fuel to lubricate the engine and reduce wear and tear, but petrol’s corrosive and your engine’s not designed to withstand it.

The damage can be far-reaching and could lead to you needing to replace the whole fuel system, which is as expensive at is sounds.

If you put petrol in a diesel car and start the engine without realising, there can be signs such as a noisy engine, struggling to start the engine or the engine doesn’t stop once its running.

It’s best to avoid starting your car after you misfuel as it can prevent further engine damage.

Is it possible to put diesel in a petrol car?

Yes, unfortunately this is also a more common problem than you might think. While the diesel nozzle is bigger, making it harder to fill a petrol car with diesel, it’s by no means impossible.

If this happens, the diesel will clog the fuel system and stop the car from starting. The fuel tank must be drained to protect your car from any damage.

Can I fill my car up with E10 petrol?

E10 fuel has 10% renewable ethanol, it reduces CO2 emissions associated with petrol cars. About 95% of petrol cars can use E10 fuel - check if yours is compatible.

If your car takes petrol and you accidentally fill it with E10 fuel, there may be no harm if your vehicle’s compatible. If it’s not, there’s no need to be alarmed, just make sure you fill it with E5 petrol once you’ve used up a third of the tank.

It’s another story if your car’s a diesel, however. Filling up with E10 can have the same impact on your engine as misfuelling with regular unleaded petrol.

What steps can I take to avoid misfuelling?

  • Don’t get distracted when you’re at the pump.
  • Check the label of the pump you’ve picked up.
  • Your car may have a sticker inside the fuel cap with the name of the fuel. If it doesn’t, add one yourself to remind you.
  • Before you start filling, check the labels on the pump and fuel cap are the same.
  • Installing a misfuelling prevention device or cap may be useful if you regularly use different cars with different fuel.

Does my insurance provide cover for misfuelling?

Flow car insurance covers you for putting the wrong fuel in your car. We pay to drain and flush your fuel tank, as well as cover the damage to the car’s engine*

*You may have to pay an accidental damage excess – we’ll tell you how much that is when you phone to make a claim.