Petrol in a Diesel & Diesel in a Petrol Car – What to Do

So you’ve put petrol in your diesel car. Or, you’ve put diesel in your petrol car. Or maybe you’re just nervous about making this mistake.

In any case, this is your guide to what to do if you put the wrong fuel in your car – and how you can take steps to avoid making this mistake in the first place!

Help! I’ve Put the Wrong Fuel in My Car!

If you’ve put the wrong fuel in your car:



Any way you cut it, putting the wrong fuel in your car is a costly mistake to make. But you’ll really do some damage if you try and drive your car having topped it up with the wrong fuel.

What To Do If You Put Petrol in a Diesel Car, or Diesel in a Petrol Car

If you’re lucky, you’ll realise you’ve made a misfuelling mistake early. Many agree that you can mix up to 5% petrol into a diesel car without doing too much damage.

Stop pumping immediately

So if you’ve just started pumping, and you realise you’re pumping the wrong fuel, stop immediately. Again, don’t start your car. Don’t even turn your key in the ignition. If the dashboard lights come on, it might indicate that your fuel pump’s already in action. This will just add to your problems.

Tell a member of staff at the garage

Tell a member of staff at the garage that you’ve made a mistake. They may be able to cone off your car so you don’t have to move it.  If you are a member of a breakdown company you should call them to arrange help.  Some petrol stations may be able to call a specialist to come and drain your tank. This will cost you about £200. And that might sound like a lot of money, but it’s nothing compared to what you’d have to pay were you to drive your misfuelled car.

If you’ve driven your car, call for help immediately

If you drive your car after misfuelling it, there’s no guarantee that you’ll do significant damage.

Most likely, your car will stutter and stall a few minutes after you’ve left the garage. Call for help immediately – either your breakdown assistance or a misfuelling specialist.

Describe the problem and, if you’re lucky, they’ll be able to help you before the fuel’s had a chance to do any lasting damage to your engine.

Put petrol in a diesel car? What happens now

If you actually drive your car with the wrong fuel, in the worse case scenario, you might have to:

  • Have your tank drained
  • Flush your fuel lines
  • Drain your engine
  • Fix potential lubrication issues

Modern diesel engines rely on diesel itself to act as a lubricator. Petrol won’t lubricate in the same way, which will result in a lot of gnashing, grinding and attrition in your engine. All of this is going to cost you.

Petrol can also be more corrosive than diesel. If it’s allowed into a diesel fuel system, it’s going to damage the fuel injectors and corrode countless seals. The ultimate bill for flushing, cleaning, inspecting and repairing your engine could rack up to thousands upon thousands of pounds.

Which is Worse: Petrol into Diesel or Diesel into Petrol?

It’s actually pretty uncommon to put diesel into a petrol car. Diesel pumps have wider nozzles that are simply too big for the majority of modern petrol cars. It’s rare to misfuel a petrol car, because most people realise their mistake before it’s too late.

But putting petrol into a diesel car? That’s a surprisingly easy mistake to make, and it happens more often than you might think.

How to Avoid Ever Misfuelling Your Car

Like we said above, this mistake is more common than you might think. When you’re tired, or distracted, it’s all too easy to do things on autopilot. And when you do something as monotonous as topping up fuel on autopilot, you can add the wrong fuel to your car without even realising it.

Whenever you do anything with your car – whether it’s driving it or servicing it – you’ll need to be totally on the ball. Accidents happen when you let your attention wander. So perhaps you could make a point of never refuelling when you’re tired? Do it at the start of journeys, rather than the end, when you’re feeling as fresh as can be. You could also put a little sticker by your fuel cap, to remind you of what sort of fuel your car needs.

And if you really want to safeguard yourself against such costly mistakes, we can add misfuelling insurance to your comprehensive car insurance policy. For more information about what this will cover, please read your policy wording.


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