Don’t turn on the ignition or start the engine
If you’ve put the wrong fuel in your car, don’t turn on the ignition or start the engine as this will circulate the contaminated fuel and increase the risk of expensive damage.
If you have just accidentally put the wrong fuel in your car you’re not alone. At least 150,000 drivers put the wrong fuel in their car every year. That’s one every three and a half minutes.
‘Misfuelling’ seems to be associated particularly with 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.
