Put Petrol in a Diesel Car? 14


If you’ve just put petrol in a diesel car I’m sure that first thing you want is sound advice on what to do next. There are a lot of opinions out there on how you should treat your vehicle after a misfueling, and to be honest, most of it is worthless. My knowledge on the subject is a result of extensive experience dealing with misfueled vehicles. I have spoken with many tens of thousands of motorists who have put petrol into their diesel vehicles, and a few thousand who have put diesel into petrol. Additionally, as a company we have completed fuel drains on many, many thousands of misfueled vehicles. This is our business and is pretty much the only thing we do – therefore we are professional specialists on the subject. With all that in mind, I’m going to give you some advice on what to do and what the common untruths are.

I’ve filled up my car with petrol instead of diesel and drove it until it conked out. Have I ruined it?

It is very unlikely that you have ruined your car by misfueling and driving it. That said it’s not unheard of for a pump to fail, or an injector to get clogged. But, statistically speaking, of the more than 4,000 fuel drains we have done so far this year on run misfueled vehicles, less than 10 had sustained damaged necessitating a visit to a garage for repair (less than 0.25%). In the cases of damage the vehicles had generally been run continuously, long after the misfuel was known about, and the customers had tried to just “get away with it”.

I’ve misfueled my vehicle and the dealership has told me I need to replace almost the entire fuel system. Is this true?

No. Well, if it’s not true why do people say it? The answer to that is very simple – money. If you put petrol into your diesel Mercedes, for example, and take it in to the dealership you would likely be faced with a bill to the tune of thousands of pounds. Mercedes will say that because there is a possibility that some parts have become damaged (regardless of how remote that possibility is) they are no longer able to guarantee those parts. Therefore, in order for them to be able to maintain your warranty and continue to guarantee your engine parts they will need to replace them. Not only does this protect them from an unsatisfied customer suing when their engine fails it also makes them a tidy little sum of money.

A few months ago we did a fuel drain on a brand new Mercedes C Class. The customer had put petrol into it and then moved it from the pump to a parking bay at the petrol station. It was then recovered to the dealership and he was given a bill for £750 to drain the fuel out and £9,000 to replace the “damaged” engine parts. We attended the vehicle, drained it and cleaned it out for the customer for a tiny fraction of that amount. I spoke with the customer recently and he has had absolutely no problems with the vehicle at all. So, did he really need to have everything replaced? I leave that for you to decide.

I’ve only put a little petrol into the diesel tank, less than 10% of the fuel tank’s capacity. Can I just top it up with the correct fuel?

You hear a lot of this going around. And you also hear a lot of conflicting stories and opinions on its validity. There are probably as many correct answers to this as there are cars in the world. I’ve heard of people having a 10% contamination problem and filling the vehicle up and never experiencing a problem at all. I’ve also been called out to help stranded motorists who put less than 5% petrol in their diesel and the vehicle conked out. I think I can best explain it with an analogy: Liken misfueling to putting drugs into the body. Pretty much everyone reacts differently to drugs. Some can have a little with no serious adverse effects. Some can’t handle even the smallest amounts. Anyone will die if you give them too much.

So, when deciding whether to “fill it up and give it a go”, just realise that it’s a gamble. How lucky do you feel?

If you are still unsure of what to do after putting petrol into your diesel car, give us a call. We’d be glad to help.

 

 


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14 thoughts on “Put Petrol in a Diesel Car?

  • Richard White

    I have just mis-fuelled my 2.0TDI VW engine. (2010) model. The tank had about 10 litres of Shell V-Power in it and I put in 2.3 litres of V-Power unleaded before I realised. I have taken a chance and put in another 40 litres of V-Power diesel. The engine ran fine the five miles home. Do you think I’ll get away with it if I keep topping up?
    Richard.

    • TheFuelMan Post author

      Hi Richard,
      You might as the contamination ratio, especially if you brim the tank with the correct fuel, is very low.
      However there is always a risk involved. Here’s an excerpt from another post I wrote on the subject:
      What Happens if I put the Wrong Fuel in my Car?
      “I’ve seen vehicles running well with almost 80% contamination. And I’ve also seen vehicles break down with as little as 3% contamination. With all the variables in the mix, driving a car on the “wrong fuel” is a gamble – with ever increasing odds against as the contamination percentage goes higher. In fact the odds are so heavily stacked against it working out ok that the majority of modern dealerships will no longer guarantee their parts if they have come into contact with the wrong fuel. Yes – that means that taking a misfuelled vehicle back to most dealers will result in a bill for an entirely new fuel system. I’ve seen Mercedes and Land Rover / Range Rover bills in excess of £15,000 just because of 10 litres of the wrong fuel.”
      I hope this helps.
      The Fuel Man

      • Richard White

        Hi, further to my previous message concerning mis- fuelling my VW CC TDI, (2.3 litres of unleaded in the tank) I brimmed the tank with V-Power diesel and I’ve kept it topped-up ever since to keep diluting it and have had no problems. The engine has never missed a beat, so fingers crossed, it’s looking okay!
        Hope this helps anyone else.

  • Ray MacDonald

    Hi, i have just put 30 pounds of petrol in my freelander2 TD4. i ran it for roughly 200 meteres where it statred to chug. i returned to the garage and filled the tank up with diesel £54 pounds. There was roughly 50 miles of diesel in the tank before filling with petrol. I then ran the jeep for an hour and topped up then again in afternoon and topped up. I continued to do this for 5 days driving 1 hour a day and topping up which put another £60 pounds of diesel in the tank. The jeep seems to be running okay now only after first night that the engine rattled a little and got some smoke from the exhaust. I have now came offshore and it won’t be getting run the same as wife will only be running it round town. Do you think i have done any serious damage.

    • TheFuelMan Post author

      Hi Ray,
      Freelanders are sturdy vehicles and can generally take a lot of beating. Had you done the same to a lesser car you wouldn’t have got that far.
      My advice in this situation is always to drain the vehicle when we are talking about such a quantity of unleaded (think of it as 10 2litre milk bottles and you get the idea of how much it is).
      As regards any damage done I would suggest that you have dramatically shortened the life-span of your fuel system components. Running petrol through them continually for days on end will wear them much faster than normal use.
      Is a fuel drain necessary now? Probably not as you have already diluted it out. But if I were you I would get the fuel filter changed – just in case – as well as use a lubricating additive in the fuel to help restore the fuel system to its proper condition.
      Hope this helps.
      The Fuel Man

  • Shannon

    Hi
    My husband just filled 3/4 of the tank in our 2011 Nissan Navara diesel with petrol. I realised immediately that the wrong fuel had been put in when I went to pay. By the time I rushed back out to tell him he had turned on the vehicle and it had idled for about 10 secs but he had not accelerated or moved the car. We turned the car off straight away and it was towed to our dealers where it is now sitting to be drained next week. Is there likely to be any damage, and is it likely that the petrol has made it into the fuel lines and filter? Thanks

    • TheFuelMan Post author

      Hi Shannon,
      Unfortunately there is a high possibility that the contaminated fuel will have reached through the entire fuel system. However, due to the length of time it was run, there is practically no chance that there has been any damage caused. I wouldn’t worry about it at all.
      One thing that I would watch out for is if the dealership decides that you need to replace all your fuel system components. In 99.8% of cases this is not necessary at all. Additionally, you shouldn’t be looking to spend more than £200 for the fuel drain and flush.
      Wish you the best of luck.
      The Fuel Man

  • Kamrunchowdhury

    May brother filled up my bmw x3 55 2.0d with £25 unleaded already had diesel in it and then realised what he did and topped it off with another £25 diesel, he then drove 100 miles what are the consequences to the engine. I am so upset as only had car for 6 months. He is having it flushed out but I want to know what long term problems it may cause as the garage didn’t say anything. Please help

    • TheFuelMan Post author

      Hi there,
      As regards long-term damage what you are probably looking at is reduced lifespan of your fuel system components. Whereas they should last 10 years or so, they will probably need to be replaced sooner than that due to the extra wear and tear on them. I would definitely suggest that you have the fuel filter replaced because it will most likely be compromised due to the amount of petrol flowing through it.
      However, if you had te vehicle drained and flushed completely there should be no further damage to the engine.
      Hope this answers your question.
      The Fuel Man

  • Robbie

    I have a 63 plate diesel VW Golf. I bought fuel at a petrol station, 10 litres only because I already had about 25 litres in the tank just to get me home making sure it was from he diesel pump and drove off with no problems or any noticeable changes to he engine sound. I reached my destination some 12 miles later. When starting the car some 15 minutes later it started but a bit high reved before it starts. I checked the receipt to make sure it was diesel I put in the tank. From reading all the threads online I am worried it may be contaminated fuel, a mix of petrol. Please advise.

    Scared

    • TheFuelMan Post author

      Hi Robbie,
      I’m not sure what the symptoms your vehicle is suffering from, other than starting at higher revs than normal. If you have checked your receipt and found nothing amiss then you are probably ok. Obviously it is possible that the fuel could be contaminated – this is not unheard of. However, if that were the case you would surely be experiencing a few more problems.
      Are there any other symptoms?
      The Fuel Man

  • Mathew

    Hello Fuel Man,
    I have gone through the entire thread and comments posted by the people related to the fuel mix up. First thing is, I would like to thank you very much for providing a very nice information and quick guide to resolve the common issue.
    Well Coming to my issue, I drive a SKODA RAPID 1.6TDI. I had put some diesel in the tank from a barrel unknowingly that the tube used to pump diesel in my rapid had some water left in it. After I drove for a 70 odd miles, my car suddenly gave a vibration and stopped in the park way. Immediately I called up the SKODA dealer and they took the vehicle to their dealership. The service guy has called me up and said that the entire fuel subsystem has damaged and it has to be replaced which will cost me 4000£. I was paralyzed for a moment and stuck up on what to reply him. I replied him that I will make it to the dealer tomorrow and check what’s all wrong.
    Do I really need to change the fuel system or shall I just ask him to fix my older parts and start using the car..?
    Please help me out of this thing.
    Thanks in advance

    • TheFuelMan Post author

      Hi Mathew,
      It is very unlikely that the entire fuel subsystem needs to be changed. You will definitely need the filter changed but I can’t see how or why they will need to do more than that – other than flushing the lines and clearing out the tank.
      I would find out exactly what needs to be replaced – specific part – and find out why; what’s wrong with those parts. It could be that the dealership is telling you this because they feel they need to replace everything just so that they can maintain the warranty, without anything actually being wrong. If I had a pound for every time I’ve heard this story I’d be a rich man.
      If getting them to see this doesn’t work I would get the vehicle recovered from the dealership and get an “independant” evaluation. A fuel drain and flush will cost you a tiny fraction of this amount.
      The Fuel Man