Misfuels happen in a hurry, usually at a busy station on the A33 or the A4, and usually because the nozzle felt the same as last week. Petrol in a diesel is the common one. Diesel in a petrol happens too. The next thirty seconds decide whether this is an afternoon inconvenience or an engine rebuild.
Do not start the engine. Do not even turn the key to accessory if you can avoid it, because some cars prime the fuel pump at that point. Put the car in neutral if it is safe to roll it off the pump, switch on the hazards, and call a recovery team that drains tanks rather than just tows cars.
If you have not started the engine, we drain the tank at the station or recover the car a short distance and drain it on the bed. The lines are flushed where we can reach them, the correct fuel goes back in, and most cars drive away the same day.
If you have already started it, tell us immediately and honestly. A short crank is often still a drain-and-flush job. A drive down the A33 with the wrong fuel in a common-rail diesel is a different conversation, because the injectors and high-pressure pump may already be damaged. We will still drain it. We will also tell you if a garage needs to look at the injection system before you drive it again.
The cost of a drain is a fraction of the cost of a driven misfuel. Anyone who tells you to “just fill the rest with the right fuel and it’ll dilute” is guessing with your engine. Ring us from the forecourt. We would rather talk you out of starting it than invoice you for a pump later.