What to do after putting the wrong fuel in your car

Here we explain any prospective damage and run through your options, so you know exactly what to do next.

Have you turned the ignition yet? If not, don’t!

The most serious damage from misfuelling occurs after turning on the ignition. 

So if you realise you’ve put the wrong fuel in your car before starting your engine, you’re in luck. Here’s what you should do:

1. Leave your engine switched off and avoid putting your key in the ignition
2. Let staff at the petrol station know what’s happened
3. Put the car in neutral
4. Push the car to a safe place
5. Call breakdown cover or RAC Fuel Patrol to drain and flush your fuel system
6. Call your insurance provider as soon as possible

If you’ve started your engine after filling up with the wrong fuel you should:

1. Turn off the engine immediately if it’s safe to do so. If not, pull over to a safe spot
2. Put the vehicle in neutral
3. Call breakdown cover or RAC Fuel Patrol to drain and flush your fuel system
4. Call your car insurance provider as soon as possible

The RAC's wrong fuel recovery service drains the tank and fuel system of contaminated fuel and provides you with enough clean fuel to start moving again.

Our fuel patrols are trained mechanics and hold accreditation to allow them to work safely on petrol station forecourts, so you don’t have to worry about where you’ve stopped your car.

Specialists can even tow away your vehicle if the damage is too great.

Call RAC on: 0330 332 8456

Whether it’s putting diesel in a petrol car or vice versa, this common mistake happens around once every three minutes in the UK and is easily done when not paying full attention at the pumps. 

The unfortunate reality is the error can end up proving rather costly, as fuel systems may need to be completely replaced. But that’s not always the case.

• Stop-start engines and engine idling – the law and common myths revealed
• RAC Fuel Watch: Petrol and diesel prices
• Towing a car – tips and rules for towing

If you’ve used petrol in a diesel car you might notice:

• a loud knocking sound while accelerating
• excessive smoke coming from your exhaust (exhaust repair)
• slower than usual acceleration
• the engine warning light illuminating
• the engine stopping altogether
• your car struggling to restart 

If you’ve used diesel in a petrol car you might notice:

• your engine misfiring
• excessive smoke from your exhaust 
• your engine cutting out
• your engine failing to restart

Putting petrol in a diesel car is far more serious than putting diesel in a petrol car. 

However, you can limit the damage to your engine by leaving it switched off and your keys well away from the ignition.

We’ll run through common misfuelling damage to both car types below:

Diesel cars use fuel as a lubrication oil, ensuring engine parts run smoothly to prevent wear and tear. 

When petrol is added to diesel the mixture acts like a solvent, dissolving the lubricant. Switching on your ignition circulates the mixture and increases friction between components, damaging parts including your fuel lines and pump.

If you do need a repair, they are often expensive and you may need to replace your entire fuel system.

Find an RAC approved garage from our trusted network, or use a RAC Mobile Mechanic, whether you need repairs or you just need to book a car service or an MOT.

Putting diesel in a petrol car is less serious than putting petrol in a diesel car.

After starting your engine, the diesel will coat spark plugs and the fuel system, which often leads to misfiring. Your engine may give off smoke, cut out, or fail to start at all.

You should drain the fuel system as soon as possible.

Pumps across Britain could start filling cars with E10 petrol from 2021 in an attempt to reduce the nation’s carbon emissions.

However, there could be as many as 600,000 vehicles on our roads that aren’t compatible with the fuel.

The RAC understands that if you put E10 fuel in an incompatible car it will still run, but seals, plastics and metals may be damaged over longer periods as a result of bioethanol's corrosive properties. 

There have also been reports that E10 is a less stable fuel and that this can make it more difficult to start a vehicle that has not been driven for an extended period.

Putting E10 in an older car shouldn't be a disaster - just fill up with a compatible fuel as soon as you can to reduce the amount of E10 in your car's fuel system.

If your car is having trouble starting, though - you should call for recovery if you have breakdown cover.

Find out more about E10 fuel.

Contact your local mobile mechanic if you're struggling with fuel recovery