Filled with the wrong fuel?

Don't turn on the ignition or start the engine. Call 0800 072 7420 or 0121 535 7479 for help

Filled up with the wrong fuel?

Filled up with the wrong fuel? Call AA Fuel Assist on 0800 0727420 or 0121 535 7479

If you've accidently put the wrong fuel in your car, don't turn on the ignition or start the engine. This will circulate the contaminated fuel and increase the risk of expensive damage.

You wouldn't be alone. At least 150,000 drivers put the wrong fuel in their car every year. That's one every three-and-a-half minutes. It could be a result of being new to the vehicle or simply being distracted while filling up.

Do you need immediate help?

Call 0800 072 7420 or 0121 535 7479.

'Misfuelling' seems to be associated particularly with the growth in diesel car sales. Modern diesels are so quiet it's easy to forget you're driving one, particularly if it's a second family car or hire car.

Potential damage

Diesel fuel pumps operate on very fine tolerances and at very high pressures – modern systems run at between 350 and 1600 bar) – and are lubricated by the fuel. Petrol in diesel acts as a solvent, reducing lubrication, and can cause damage to the pump through metal to metal contact.

Metal particles from the damaged pump can be deposited in the fuel causing further damage to the rest of the fuel system.

Some fuel system seals can be affected by the compounds in petrol too.

The further the contaminated fuel goes in the system the more expensive the repair. In some cases it can be cheaper to fit a new engine!

Common rail (or HDi) diesel engines are particularly vulnerable – if fuel contaminated by pump wear debris gets as far as the common rail system you may have to replace the low and high-pressure fuel pumps, injectors, fuel rail, line filters and the fuel tank.

Gasoline Direct Injection (GDI) petrol engines are particularly susceptible to damage too.

Many cars have a low-pressure electric pump in the tank which starts to work as soon as the ignition is switched on, circulating contaminated fuel through the pump and rail, so it's important not to turn the ignition on.

Petrol in diesel

  • Don't turn on the ignition or start the car
  • In line with car manufacturers' recommendations, AA advice is that any diesel fuel contaminated with petrol should be removed from the tank and replaced with clean fuel before the ignition is turned on and the car started.

Diesel in petrol

  • Don't turn on the ignition or start the car
  • This is less common because the standard diesel nozzle is bigger than the filler neck on modern petrol cars.
  • In line with car manufacturers' recommendations, AA advice is that any petrol contaminated with diesel should be removed from the tank and replaced with clean fuel before the ignition is turned on and the car started.

AA Fuel AssistSM

Fuel Assist is a specialist roadside service that drains, flushes and replenishes vehicle fuel systems on the spot, saving you time, money and inconvenience.

Fuel Assist is available to the general public as well as to AA Members. We will attend any vehicle providing the Fuel Assist van has enough capacity in its tanks.

Reduce the risk

No one misfuels deliberately and no one expects it to happen to them, but around 150,000 motorists put the wrong fuel in their vehicle every year.

Misfuelling mostly involves petrol in diesel as the petrol nozzle is the smaller of the two, but a significant number of drivers still manage to misfuel by putting diesel in petrol, even though the nozzle is considerably larger than the filler neck! This suggests a high level of distraction and/or strong visual cues convincing the driver that they're dispensing the correct fuel.

Always double check the fuel grade indicator on the pump before filling.

The risk of misfuelling is higher if:

  • you use an unfamiliar filling station - don't assume hose colours are the same as your 'local' site
  • you switch between brands using different hose/nozzle colours
  • you swap cars (using different fuel) at home or work - it's easy to 'forget' which car you're filling
  • you hire a car using different fuel to your normal car
  • you buy a new car using different fuel to your old car
  • you continue a conversation with passengers while filling up
  • you are in a hurry/running late

If you're concerned about the risk of misfuelling you can buy devices to fit into the (diesel) filler neck to prevent you inserting the narrower petrol nozzle.

(Updated 19 November 2014)