Put the wrong fuel in your car? Three things to do before you panic

Car ownership advice
Have you put petrol in a diesel car? Don't panic.

Whether it’s because you’re driving a car that you’ve not used, the pumps weren’t clearly marked at the petrol station or you just had a momentary lapse in concentration, putting the wrong fuel in your car is easy to do.

Unfortunately, it always seems to happen at precisely the wrong time, leaving you late for work, or that first meeting with the new in-laws. or that plane that’s leaving in an hour.  And though you can’t magically undo what you’ve done, with a bit of common sense and calm, you can prevent the wrong fuel doing more unnecessary damage to your vehicle by following these easy steps.

1. Do not turn on your engine

Occasionally you won’t realise that you’ve put the wrong fuel in your car until you’re halfway down the motorway and your engine suddenly starts to lose power.  And if that’s the case, all you can do is call a breakdown assistance service and wait for them to come to the rescue.

However if you realise that you’ve used the wrong fuel before you’ve turned the engine on, then you’re in luck and could save yourself a lot of time and money.  This is because the moment you turn the engine on the fuel is drawn up into the system, further damaging your engine.

If your car normally runs on diesel, the fuel pump will ordinarily be lubricated by the diesel in order for it to run smoothly. However the petrol will act as a solvent, removing the lubrication and causing the metal parts to grate against each other.

If you put diesel into a petrol car, the potential damage isn’t as severe but it will still cause your engine to smoke a bit and run badly, so it’s best to get the diesel out as soon as possible.

By not turning your engine on you can save yourself a lot of hassle and make the repair man’s job a lot easier.

2. Calculate how much of the wrong fuel you have put in

Is this person putting the wrong fuel in this car?Although it’s normally best to drain all of the fuel from your tank when you use the wrong fuel pump, if you realise your mistake while you’re still pumping, you may be able to get away with not calling out the repairman.

When you realise that you’ve used the wrong fuel, try to calculate how much you’ve pumped in. If it’s less than 10% of the tank capacity you should just be able to top up with the correct fuel and drive away.  However, if you’re unsure how much you’ve pumped in it’s always better to be safe than sorry and get the entire tank drained.

3. Call for assistance

Last but not least, you need to call your breakdown service to come and save the day.  Unless you’ve got some reliable mechanical skills, this job really needs a professional, so always call a reputable service to get you back on the road as fast as possible.

Although your breakdown service may be able to fix your car at the side of the road, if you’ve put a lot of the wrong fuel into your car, they may well have to transport your vehicle to a garage where they can carry out the necessary repairs more easily.

Putting the wrong fuel in your car is by no means unusual – in 2008 around 13 UK drivers an hour made the mistake – so if it happens to you, just remember to stay calm, keep your engine switched off and call the professionals.

You should also read: Premium petrol and diesel – are they worth the money?

Put petrol in a diesel car? Don't panic if you have put the wrong fuel in your car

This article was written on behalf of Auto Fuel Fix by Jenna Evans. Auto Fuel Fix are specialists in draining the wrong fuel from engines.

28 Comments

  1. Great advice for anyone to follow if they find themselves in that predicament. I just wished I had noticed doing the exact same thing 20 years ago before I drove off in my car. It would have saved me a couple of hundred pounds.

    Reply
    • I used http://www.wrongfuel-recovery.co.uk and I would recommend them. I had actually driven the car for 20 miles before I realised what I had done (petrol in diesel car) so don’t think it’s £5000 if you are in the same predicament – it cost me £143.00. Tell them how far you have driven, how much fuel was in the tank already and how much of the wrong fuel you put in. Check your receipt if you are not sure if you made a mistake – it shows that you have put in petrol or diesel – if it does not, you have only got the credit card receipt. Tip: try to have cash as they charge you 5% to use a credit card.

  2. I’ve put Diesel in my petrol ford fiesta £10 to be exact cut straight out in garage, had to be pushed out onto the dual carriageway, turned it over about 4 times in total will it damage the engine will i be ok to fill it tomorrow with unleaded.

    Reply
    • Stuart Masson

      Hi Paula. The diesel could significantly damage your engine if you continue to try and run it. The safest way to protect your engine is to have it professionally cleaned out, which is expensive.

      You may be able to get away with filing the tank with petrol, and continuing to top it up with petrol as soon as the tank drops to about 3/4 to keep diluting the diesel down. The car will probably run very roughly for a while, and there is a risk that you will damage the engine by doing do – which would be far more expensive than the cost of cleaning out the system in the first place.

    • I’ve ran all the gas out that wasn’t supposed to be used to I need to buy anything to put in the tank to flush it ,before I put the right gas in my tank?

  3. help me i pumped 1.5ltre petrol on my disiel engine mazda famaliar.i then put ten litre of disiel top up.are there any dangers of damaging the car.

    Reply
    • Stuart Masson

      It is possible that you will damage the engine if you drive the car with petrol in the tank, so the safest bet is to get the tank drained and flushed professionally. This will probably cost a few hundred pounds.

      If you want to chance it (not recommended), you need to fill up the tank with diesel to dilute the petrol as much as possible – just putting in 10L of diesel isn’t enough. Every time the tank drops to 3/4 full, top it up again with diesel to keep diluting the petrol further and further. Over a few fills, the amount of petrol in the tank will reduce until it is insignificant. The car will probably run rough and sound terrible for a while, especially when cold. Once again, you do risk very expensive damage to the engine if you so this, so it is much safer to have the petrol removed professionally.

  4. If petrol was put into a Diesel engine, how much mileage could you do before noticing problems, say if tank was near empty and got fully filled with wrong fuel without you realising??

    Reply
    • Stuart Masson

      Hi Sarah. You would almost certainly find that the car would fail to start at all, or run very poorly. You cannot drive the car or you will cause significant damage. It will have to be completely drained, flushed and cleaned out. This is not a cheap process, but it is a lot cheaper than a new engine.

  5. I have put diesel in my petrol car didn’t realise till it cut out I have now drained tank can I just fill up with petrol and run

    Reply
    • Stuart Masson

      The safest bet is to have the system professionally flushed, which will probably set you back a few hundred pounds. If you have already drained the tank, you may be able to fill it up with petrol and not have any problems, but you are at your own risk.

  6. i have mercedes gla 2016 diesel. i accidentally put in £10 petrol in (8.89 litres) the fuel light was on so may have only had 5 liters in the tank. i then filled it to the top with diesel (39.95 litre) i drove it home around 4 miles and it seemed fine. will the engine be ok or do i need to have it drained?

    Reply
    • Stuart Masson

      Hi Sharon. Ideally, you should have it drained and cleaned out, as that is the best way to ensure you are unlikely to have any problems.

      However, in a strictly unofficial capacity, you are probably going to be OK. You should definitely keep topping up the tank with diesel for a few hundred miles, so every time you drop below 3/4 full, top it up again. This will keep diluting the petrol down. You may still find it difficult to start in the cold weather for a little while.

      Bear in mind that if you do have any problems and you haven’t had the tank drained and cleaned, you may have trouble with any warranty claims on the vehicle over the next three years. Misfuelling generally isn’t covered by new car warranties anyway, but if you fail to take correct action when it happens, you are potentially making it more difficult to get assistance for other problems.

  7. Thank you Stuart.
    I couldn’t sleep last night worrying!!
    I have driven it today for around 10 miles and it seemed ok. But with it turning cold I don’t know if it’s better to just have it drained. Can they still drain it even though I’ve driven it?

    Reply
  8. Thanks for getting back to me…Couldn’t sleep last night worrying. Is it better to gave it drained with the weather turning cold. Also can It still be drained..I drove it today for around 19 mikes and it seemed ok

    Reply
    • Stuart Masson

      As with my previous comments, official advice from anywhere (including here) will always be to get it drained. This is as much of an arse-covering exercise as anything else, as no-one is going to take responsibility for advising you not to bother if it subsequently blows up. And it is the best way to get absolute peace of mind.

      However – unofficially – if you have driven the car for about 20 miles in total now with no real problems, you are probably going to be OK. If the car was not happy with the fuel, it is likely to have been noticeable by now. If you keep topping up the tank with diesel to continue to dilute it down for the next couple of weeks, you should be fine. The engine’s on-board computer automatically adjusts for poor quality fuel anyway (as not every country is as strict as the UK on fuel quality), so it is likely to be able to cope with a very low level of petrol in the mix.

  9. Hi my Dad in his 80’s is complaining of rattling noise from new Nissan Juke. Could he have put diesel in this petrol car? Would it cause a noise? He previously had diesel cars. He said he drove fine for a few miles then there was awful noises.

    Reply
    • Stuart Masson

      Hi Jacqueline. It’s entirely possible, but there are many faults or problems which could cause the car to make “awful noises”. Regardless, he should get it to the dealer to have it looked at ASAP.

  10. I put diesel in my petrol mercedes aclass, put about £25 and drove it for 15 mins, got home to realise it and called my breakdown service, car got towed on the 23rd december it is now the 28th december and i had a call saying it would be £1000 then the guy realised i disnt put petrol in a diesel car but the other way round and they qoutes me £4000 am i being ripped off by mercedes. They are wasting time not answering my calls. I have spoken to garages and fuel drainers and ut would cost me £160 to drain it then replace the fuel. What should i do.

    Reply
    • Stuart Masson

      Hi Dilber. I guess it depends what action the Mercedes dealership is planning to take over and above a drain and flush for that price. £4,000 suggests significant engine damage has occurred and needs to be repaired, but they would need to have examined the engine in detail before quoting that.

  11. Hello I have put 97 instead of 87 on my car and it running rough right now my gas is almost finish in the car ? Should I wait till it finish and put back my 87 inside my car ? Bc it 335 dollar to clean out the tank do u have any other option ? Should I run out my gas then put my normal gas oil in it ?

    Reply
    • Stuart Masson

      Hi Marie. Putting higher-octane fuel in your car does not normally cause any problems; normally it’s the other way around.

      If you want to avoid draining and cleaning your tank, you should be able to keep topping up with regular unleaded to dilute the premium unleaded down. There’s no need to wait until the tank is empty.

  12. Put 87 instead of 89 in my Volkswagen what should I do

    Reply
    • Stuart Masson

      Hi Chaney. I assume you are in North America or elsewhere, as European countries do not sell either 87 or 89 octane fuel. This is a UK site, so the information here may not be applicable to your circumstances.

      However, you probably won’t do any long-term damage to your engine if you have only put one tank of 87-octane fuel in your car. What you should do is keep topping up the tank with 89-octane fuel as soon as your tank drops to about ¾ full. That will gradually dilute the poorer-quality fuel down over time.

      If you notice that the car is not running cleanly or exhibiting any problems, you should stop immediately and call your local breakdown service to recover the car and drain the tank. But this is not likely to occur if this was the first time you have put 87-octane in by mistake.

  13. Hi Stuart,

    I need your advice I mistakenly put a 7ltr fuel into my diesel engine Mercedes-Benz 2001 CDI W203 when I find out I was advised if I put a 30ltr diesel it will be fine but after a while my car started smoking terribly and had to drain the whole gas out what do I do next to stop the smoking.

    Reply
    • Stuart Masson

      You will probably need to have the entire fuel system cleaned and drained. Even with the fuel tank drained, there can be a considerable amount of fuel in the rest of the system (pipes, pumps, etc.).

  14. Dear Stuart
    It gives me great pleasure to thank you and complement for your valuable advise to the readers.
    This morning only my wife rang to inform me that she has accidently put about 5 litres of patrol in our diesel Citroen Berlingo She was advised at the petrol station to top up the rest of the tank with diesel and hope that no damage will occur.
    Then I read your various advises and understand it that I must keep topping up with correct Diesel fuel before the fuel gauge goes under three forth to dilute the remaining petrol.
    Obviously there is no guarantee that damage can not still occur, however I hope that this may not happen.
    if you any advise or comments please do so, meanwhile many many thanks for improving our knowledge.
    Warmest regards
    Jai

    Reply
    • Stuart Masson

      Hi Jai. If it was only five litres, then it’s unlikely to cause any permanent damage to the engine – although we would always recommend that you get the engine properly flushed and cleaned to guarantee this.

      If you plan not to get the fuel system flushed and cleaned, then by continuing to top up with diesel, you should be OK.

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