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What To Do If You Put The Wrong Fuel In Your Car

Last Updated: 12th Nov 2018
What To Do If You Put The Wrong Fuel In Your Car

12th November 2018

NOTE: WHETHER YOU’VE PUT PETROL INTO A DIESEL CAR, OR DIESEL INTO A PETROL CAR, DO NOT SWITCH ON THE ENGINE OR PUT YOUR KEY IN THE IGNITION IF YOU’VE FILLED THE WRONG FUEL

Putting the wrong fuel in your car can be an easy but costly mistake to make. According to RAC, cars are misfuelled every three minutes in the UK.

Petrol in a diesel car

This is the most common way of misfuelling as the petrol nozzle is small enough to easily fit into a filler neck on a diesel car’s fuel tank.

First and foremost, if you have put petrol in a diesel car, try not to start it. Starting your engine will circulate an emulsion of both fuel types throughout your engine which can cause more damage. Your fuel tank needs to be drained before you drive away.

Along with powering the car, diesel acts as lubrication oil that keeps the fuel pump and other parts running smoothly. The added petrol will act as a solvent, giving diesel the opposite effect - damaging the fuel pump and other components of the fuel system and could result in you needing to replace the engine.

Diesel in a petrol car

Wrongly fueling a petrol car isn’t as common as diesel pump nozzles tend to be larger than most petrol fuel necks, preventing room for misfuelling.  

If the mistake is made, putting diesel in a petrol engine is likely to cause less damage than it would the other way around. Diesel requires compression before it can be ignited, so you’ll probably find you can’t start the engine.

Again, most repairs will require the fuel tank to be drained to get rid of the contaminated fuel.

What to do if you’ve put the wrong fuel in your car

Remember, do not switch on your ignition. Ideally, you want to make sure the fuel is flushed first.

If you do realise you’ve wrongly fuelled before starting the engine, here’s what to do:

  • Keep the car turned off
  • Put the car in neutral
  • Ensure the car is in a safe spot - push it out of any danger if possible
  • Inform your insurance company as soon as possible
  • If you have breakdown cover, it is worth calling them - it’s likely they’ll be able to drain, flush & refuel your car

If you have driven off, your car will eventually come to a holt. This is then to be treated as a regular breakdown. If you have breakdown cover, ring your provider and inform them of the incident. If you’re not covered, you’ll need to call the Highways Agency for assistance.

Avoiding putting the wrong fuel in your car

Of course, the obvious solution is being more attentive when filling your tank. But other precautions can be put into place to avoid mishaps at the filling station:

  • You can buy a diesel fuel cap that fits into your neck filler. This cap will prevent petrol nozzles fitting your filler neck. Depending on the model of car, they tend to cost between £15 and £30.
  • Rather than just looking out for the colour of the hose, properly read the pump’s label.
  • Avoid refuelling when you’re in a hurry.

The wrong fuel can cause damage to your car, but the key is not to panic, keep your engine off and get the appropriate assistance will ensure you are back on the road.

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