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What to do if you’ve used the wrong fuel

How to prevent further damage to your car

If you’ve put the wrong type of fuel in your car, try not to switch the engine on or put the key in the ignition if you can possibly help it, especially if you’ve filled your diesel car with petrol. This will help contain the mixed fuel in the tank and stop it from circulating – which could cause permanent damage.

Topping up with the wrong type of fuel is a very common mistake to make, with around 150,000 UK motorists finding themselves in this predicament every year. There are several factors that affect how much damage using the wrong fuel can cause – from how much fuel you’ve put in to whether it has circulated – so you may be able to prevent further damage to your car by following the steps below.

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

If you’re still at the station:

  • Don’t start your engine or put the key in the ignition
  • Put your car into neutral and ask someone to help you push it to a safe place
  • Call a recovery vehicle and have an engineer assess the damage

If you’ve started driving:

Regrettably, the damage may have already been done. Pull over somewhere safe, remove the keys from the ignition, and call a recovery vehicle.

What happens if you put petrol in a diesel car?

Putting petrol in a diesel tank is far more common than vice-versa – mainly because petrol nozzles fit easily into diesel tanks. Unfortunately, this is also the costlier mistake.

Diesel acts as a lubricant and helps the fuel pump run effectively. Petrol, on the other hand, acts as a solvent when mixed with diesel, and has the opposite effect. The concoction will reduce lubrication and cause friction between parts, damaging both the pump and engine.

What happens if you put diesel in a petrol car?

Diesel pumps generally don’t fit in petrol tanks, so you’re far less likely to find yourself in this situation.

While diesel needs to be compressed before ignition, petrol ignites through the spark plugs. This means that putting diesel in a petrol tank will likely result in your car not starting. Although not ideal, this is a more favourable scenario and less costly than permanent damage caused by petrol in a diesel tank.

How to avoid putting the wrong fuel in your car

There are ways to reduce the chances of misfuelling and save yourself a considerable amount of money, time and bother:

  • One of the most common times misfuelling occurs is when you’ve got a new car that uses a different fuel to your previous one. It might be worth having an eye-catching reminder sticker in the car or on the petrol cap
  • Always make sure you read the pump’s label before filling up
  • Avoid distractions while filling up
  • If you own a diesel car, it could be an idea to invest in a diesel fuel cap that will prevent petrol nozzles from being able to fit in the tank. The price varies between make and model, but you can generally get hold of these for less than £30 – a small price to pay compared to a hefty repair bill

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