If you have put the wrong fuel in your vehicle, you are not alone.
What matters most is what you do next.
This what to do if you have put the wrong fuel in:
Putting petrol into a diesel tank causes more damage than diesel in a petrol car. Plus, petrol nozzles can easily fit into most modern diesel filter necks. It makes it far easier to accidentally put petrol into a diesel tank than vice versa.
Petrol damages diesel engines because: Diesel acts as a lubricant, helping the fuel pump to do its job. Petrol does the opposite - it increases friction between parts in the diesel engine. The friction is not good news for your diesel engine. The more petrol that is pumped through the diesel engine, the more damage it'll do. That is why it is so important not to start the car.
Common rail (or HDi) diesel engines are particularly likely to be damaged by the wrong fuel. If there is a lot of damage, it could mean new fuel pumps, injectors, pipes, filters, fuel tank – or even a whole new engine.
The diesel pump nozzle is bigger than most petrol filler necks, so it does not really fit. That makes it far less common to put the wrong fuel in a petrol car than putting petrol in a diesel car. Plus, it is not as bad for a petrol engine to have diesel in it so there's usually not as much damage.
Here is what happens when you put diesel in a petrol car: Petrol ignites by a spark from the spark plugs. Diesel in a petrol engine clogs up the spark plugs and fuel system. That means the car simply won’t start. It is a real pain. But it is not as bad as the damage that petrol can cause to a diesel engine. Your petrol engine should not have any permanent damage once the fuel's drained out.