Wrong Fuel in Car: Actions to Take Immediately

Filled up with the wrong fuel? Learn what to do next, key symptoms, possible damage and costs. Follow this step-by-step guide to minimize risks.

It’s surprisingly easy to make a fueling mistake — especially when you’re in a rush or driving an unfamiliar car. In the UK alone, around 150,000 drivers each year fill up with the wrong fuel. What seems like a simple slip can turn into a costly problem, ranging from a few hundred pounds for a fuel drain to several thousand for full repairs.

The golden rule is to realize the mistake as soon as possible. If you’ve just put the wrong type of fuel in your tank, do not switch on the ignition under any circumstances. Even turning the key to the ‘ACC’ position can activate the fuel pump and send the wrong fuel deeper into the system. Ideally, shift the car into neutral and push it to a safe spot away from the pump. Let the station staff know — they’ve likely seen this before and can help. Next, call your roadside assistance provider or insurance company. Some insurers cover misfuelling, but many don’t, so it’s worth checking in advance.

Things get trickier if the engine’s already running. Here, speed is your ally: the sooner you stop the engine, the better the chance of avoiding major damage. If the car keeps running, the risk of harming the fuel pump, injectors, or even the catalytic converter goes up fast. According to recent reports, repairs can range anywhere from £190 to £5,000 depending on the extent of the damage.

Spotting the warning signs helps too. For a diesel car filled with petrol, listen for knocking noises during acceleration, loss of power, unusual exhaust smoke, or a struggle to start. If it’s the other way around — diesel in a petrol engine — you might find the engine won’t start at all, misfires badly, or loses power dramatically.

Prevention is always the best cure. Experts recommend double-checking the pump label before filling up — it sounds obvious, but it works. You could stick a reminder near the fuel cap or fit a special misfuelling prevention device, especially for diesel cars — they make it physically impossible to insert the wrong nozzle.

One careless moment at the pump can lead to days in the garage and an eye-watering repair bill. But quick action and a clear head can keep the costs down. And with a bit of extra care, you’ll probably never have to deal with this mistake at all.