What Car? Q&A - Wrong fuel

Q: I’ve just bought my first diesel car, an Audi A4 2.0 TDi, but I’m worried that I will put petrol in the car by mistake. What would happen if I did, and what should I do?
David Oliver

A: Filling up with the wrong fuel happens more often than you might think. If you realise that you’ve accidentally put the wrong fuel into your car, the important thing is not to try and start the engine. If the wrong fuel is just in the tank, the car can be drained, refilled and put back on the road relatively cheaply.

However, if the engine has been started you could cause major damage. Petrol and diesel engines work in very different ways and if the wrong sort of fuel finds its way inside, you may need expensive components replacing, having the engine flushed out, or in the worst cases getting the engine rebuilt or replaced.

As soon as you realise your mistake, phone breakdown recovery, or contact the nearest garage and arrange for them to collect the vehicle.