What to Do If You Fill Up with the Wrong Fuel in the UK

Last updated: 3 August 2025

Step 1: Do Not Start the Engine

If you realise you’ve put the wrong fuel in your car while still at the petrol station — don’t start the engine. Starting the engine will circulate the incorrect fuel through the system and greatly increase the risk of damage. If the engine is off, you're in the best position to limit the harm.

Step 2: Inform the Petrol Station

Let a staff member know your car is immobile and parked near the pump. Most will understand and may help you move the car to a safer location if necessary. Do not try to push the car yourself on a busy forecourt without assistance.

Step 3: Call a Fuel Drain Specialist

You’ll need a professional fuel drain service to remove the contaminated fuel and clean your system. Many breakdown providers (like the AA or RAC) offer misfuelling assistance, or you can call a dedicated wrong-fuel recovery service. They will usually:

  • Drain the fuel tank safely
  • Flush the fuel lines
  • Refill with the correct fuel
  • Check the vehicle starts correctly

Step 4: If You’ve Already Driven Away

If you only realise after starting the engine or even driving off, stop the vehicle as soon as it’s safe to do so and switch off the engine. The longer you drive, the more contaminated fuel flows through the system — increasing the likelihood of engine damage. Then call a recovery or fuel drain service.

Which Is Worse — Petrol in a Diesel or Diesel in a Petrol?

Petrol in a diesel engine is generally more damaging. Diesel engines rely on fuel for lubrication, and petrol acts as a solvent, stripping that lubrication away. This can lead to damage in the fuel pump and injectors. Diesel in a petrol engine is usually less harmful, but still requires draining and flushing.

How to Know If You've Misfuelled

  • You remember using the wrong pump or nozzle
  • You notice the nozzle didn't fit as usual (petrol nozzles are smaller)
  • The engine struggles to start or runs roughly
  • There’s smoke or unusual smells from the exhaust
  • The car suddenly loses power after refuelling

How to Avoid Misfuelling in the Future

  • Use a fuel cap label to remind you of the correct fuel type
  • Don’t rush while filling up — double-check the pump and nozzle
  • Consider fitting a misfuelling prevention device
  • Avoid distractions like phone use while refuelling

Helpful Links

Frequently Asked Questions

Some comprehensive insurance policies cover misfuelling, but many do not. Always check your terms or speak to your insurer.
No. Attempting to drain the fuel yourself is dangerous and could damage your car. Always use a professional service.
Costs vary but usually range from £150 to £300 depending on the provider and time of day. It’s cheaper than engine repairs.