Wrong Fuel - what to do?

It’s hot, you’re tired, the kids are squabbling relentlessly in the back of the car, you need the bathroom, and you’re running on fumes. How many of us have filled up on the wrong fuel under conditions like this? About 150,000 every year, according to the AA (nearly one every three minutes).

The commonest form of misfuelling is pouring petrol into diesel (the other way around, the nozzle doesn’t fit so easily and you’ll have time to realise the error of your ways). Petrol acts as a solvent in diesel engines, reducing lubrication, and can damage the pump by causing metal-to-metal contact. And if you get the petrol nicely spread throughout the system, it’ll be cheaper to buy a new engine than repair the one you’ve just contaminated. So, what’s to be done if you’ve dropped a clanger like this on your foot?

The most important point, if you realise what you’ve done before driving away (both with petrol into diesel and diesel into petrol) is don’t turn on the ignition or start the car (you may well invalidate your warranty if you do). If you’ve added more than 10% (more than 5 litres in a 50 litre tank) of the wrong fuel, drain the tank and re-fill with the right stuff. If it’s under 10%, top up with the right fuel and drive away (unless the manufacturer advises differently). Exactly the same rules apply to diesel into petrol misfuelling.

Hopefully, once bitten, twice shy!