Land Rover Defender Blog


What to do if you put Petrol in your Diesel?

Don't panic! Here's our guide for if you accidentally put the wrong fuel in your truck.

Ben Gribbin

Ben Gribbin

December 28, 2010

Hello, I'm the editor of FunRover. I'm a massive Land Rover fan. Currently own a TD5 90. 2015 MR Blogger of the Year


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FunRover Top Tips usually sprout from us doing something completely foolish and this time, we managed to 'drop' 9 litres of petrol into the test Defender. Usually, this is a nightmare, however, we've looked into it and all is not as bad as it seems. Yes, it's daft, but there are ways to fix it. That is, depending on the amount of fuel you put in. If it's all petrol, do not turn on the ignition, simply ring up your breakdown service and have the vehicle drained properly at a workshop.

UPDATE: A few months on after this incident and the Land Rover is fine. Make sure you catch this quickly or get the tank drained. In our case, as there was so little petrol in, we took the advice of a few mechanics who told us they sometimes drop it in before MOT's to clean up the emissions. Anyway, the Landy is as good as ever and no damage has been done!


Do not turn over the ignition

If you can, the preferred method is to simply avoid turning the ignition on and calling your breakdown service. Even by turning the ignition, this could start a low pressure electric pump or sender unit circulating the contaminated fuel. Also, if the vehicle is still under warranty, phone Land Rover and ask them what the proper course of action is. We read somewhere Land Rover will replace all kinds of engine parts and even some pipes as a prevention, but we haven't been able to confirm it, so give them a ring. By not turning the ignition, you are preventing any petrol from entering the fuel lines and ultimately the engine. You can then simply drain (or have the tank drained) and re-fill with diesel (dependent on your vehicle's warranty or lack of). However, the AA suggest this is not always necessary.

Is it common rail?

If you have a common rail engine, such as on the new Defender, then this type of engine is even more vulnerable to petrol contamination. The AA suggest that "if the fuel gets as far as the common rail system you may have to replace the low and high-pressure fuel pumps, injectors, fuel rail, line filters and the fuel tank too". Hence, you can see the importance of not cranking the engine over or even turning the key. That said, if you own an older model, you may be ok...

Determine amount in tank

You may just get away with it. We've read online that petrol (in smaller amounts than you've put in probably) is used as an additive to diesel in winter, as it helps stop waxing of the fuel. The AA too suggest that if you have less than 10% of petrol in the tank, providing you brim it to the top, you should be ok. In a Defender, with a 60 litre tank, that equates to 6 litres.  If it's more, then you should drain the tank and fill it with diesel.

Playing it safe

If you're not happy with the above or wish to play it 100% safe, then the suggestions are as follows:

Drain tank (again avoiding ignition turn over, and you'll need a breakdown recovery service). Don't forget too that the fuel needs disposing of, either by paying to have it disposed of properly or using it as fuel for barbecues, lamps e.t.c. The AA run a service known as fuel assist, with dedicated fuel van drivers, who'll come and replace the fuel in the car. This is open to the general public and the AA properly dispose of the contaminated fuel, by recycling it to power concrete kilns.

But what if you've already run the car?

Again, this depends on the mixture. If you have less than 5% of a full tank of petrol, you should be fine. If it's more, then consider taking it to a qualified Land Rover specialist who will be able to take a look over any possible damage caused.

What did we do?

In our case, the car was run after taking on the petrol. Fortunately, the percentages involved mean it's pretty safe, but just to make sure, we'll drain the tank and re-fill with pure diesel. We'll also be keeping a close eye on things over the next few weeks. Of-course, in the future, just learn from our mistakes and pay attention at the pumps.

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  1. patently says:

    Do you have a recording of the “Doh!” moment when the driver realised what he’d done?

    Please? 😉

  2. TrueLandy says:

    It was a this point were all readers switched off and went else where……………..

  3. Richard says:

    (Isn’t ‘lorry fuel’ diesel..?)
    I did this at an M6 service station (name? northbound may have been Burton-in-Kendal) which used black fuel lines and black pump heads for all fuel types with ludicrously small labels on the pump head and staggered labels on the pumps themselves (I know, excuses, excuses). Since I’d filled a near empty tank with unleaded I had no choice but to call the AA – even with member discount it was over £180 if I recall, plus the cost of the wasted fuel which I had to purchase all over again. I think my mistake cost me the best part of £250. The AA guy said he got a lot of calls from that service station because of the pump design. Had they sold gerry cans I would have quietly syphoned it off I think. Needless to say I pay very careful attention to pumps now!

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