It’s one of those classic motoring mistakes which we always think happens to someone else. Putting diesel in a petrol car, or vice versa, can cause serious damage to your engine. The obvious solution to the problem is to pay a bit more attention when you’re filling up at the pump, but that’s easier said than done. If you do realise that you’ve filled with the wrong fuel, here’s what to do to minimise damage.

Immediate Action

If you suddenly realise that you’ve put the wrong fuel in the car, don’t start the engine. This will cause even more damage. Don’t even put the key into the ignition. Go back into the petrol station and tell the attendant what’s happened. Put your car into neutral – without turning the engine on – and rope in some other customers to help you push it to a safe place out of the way. If you’re covered by one of the major breakdown companies give them a call and tell them what you’ve done. They should be able to drain the fuel out of your car, flush the system through and then let you refill with the right stuff. It’s also worth giving your insurance company a call to let them know what’s going on.

What Damage Could I Do?

If you start your engine, the type of damage which you do will depend on the error you’ve made when filling.

Petrol into diesel: diesel has a lubricating effect in the engine and eases friction. If you’ve put petrol in and start the engine, this has the unwanted effect of increasing friction and causes damage to the fuel pump. Trying to drive the car away could cause very serious damage.

Diesel into petrol: this is a less serious scenario than the other way around. Diesel combusts in a different way from petrol, so the chances are that if you put diesel in your petrol car you won’t even be able to turn it on.

Will I Be Covered By Insurance?

Mis-fuelling isn’t a standard option on all insurance policies so don’t assume that you’re covered. The same applies to breakdown cover. Many policies will include rescue and draining of the system if you get the wrong fuel, but not all. If you aren’t covered for misfuelling but have cover for regular breakdown, it is worth asking whether you can pay a bit extra in an emergency situation for someone to come out and help you.

Maintenance and Servicing

If you do require more extensive work on your car because you’ve filled it with the wrong fuel, this might be the perfect opportunity to get it serviced and booked in for a MOT check, if one is due soon. Ask the mechanic to pay particular attention to the fuel lines and pumps, and make sure the engine is running smoothly. The good news is that getting the wrong kind of fuel is something most people will only do once.