Petrol in a diesel engine

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bryntaylor | 18:48 Sun 16th Oct 2005 | Motoring
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I stupidly put petrol in my BMW series 3 diesel car.  The tank had about 1/3 diesel and I put in �6 worth of petrol before I realised.  I rolled the car of the pump and it was picked up and taken to a dealership, who have quoted �800!! (my wife did same last year and it cost �160).  A couple of friends have suggested topping up to the top with diesel and it should be OK.  (Also adding some diesel Redex).  I can't afford �800 will it be OK to just top up and go?!


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You may well get away with diluting the petrol further with extra diesel (if you want to take the chance) but why not flush the fuel tank yourself either by draining it (I do not readily know if there is an accessible drain plug) or by syphoning?

�800, I think they are trying it on. 

It all depends on how old the car is, ans how much you value it. If it's a bit of a nail, then top and go. However if a newish car then the best advice would be to drain the tank. There will not be a drain plug, because they cost money for manufacturers to fit, so you have two choices. Find where the fuel supply comes into the engine compartment, split the pipe at a joint, and using an electrical pump, (few quid from local scrapyard) and a big bucket, suck the contents rom the tank, but filler capoff first.

The other method is to lift the back of the car, find the outlet from tank, and split it there with a bit of gravity it will drain.

I imagine the local dealers are imagining you have run contam into the engine, so they are covering their backs. Try ringing and asking how much for just a tank drain, no other work.

I used to do recovery, and at least one per day would do contam(inated fuel). The charge was �100, with a gallon of fresh.

Good luck

Also very unlikely you will be able to syphon, they put a mesh across the bottom of the fillers to stop people nicking your fuel.
... or to deprive dealerships of a potential windfall.
hi byrntaylor,  Well in theory a diesel engine will run on petrol and other stuff anyway but the problem is that petrol is non lubricating and used alone will damage the fuel injector pump from lack of lubrication.  In your case your friends advice should be correct.     

bryntaylor, You need to say how old the car is. If it is a new type engine(common rail fuel system) the fuel pump will be damaged by petrol. On an older style fuel system a general guide line it 20% of the incorrect fuel,no more. If below 20% fill tank right up & keep topping up. If you drive with any petrol in  & it is common rail diesel you will end up spending about �6000 so you must be sure...

read this if the link works. I suspect from the price they have quoted it is the earlier fuel system but make sure...

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Thank you for the responses - much appreciated.  (I found a dealership who will do for �175, so gone with that!)  Shows the �800 is a total rip-off!

Hi there,

I did something very similar to this about 4 weeks ago.

I'd owned my 1996 Renault Laguna 2.2 diesel for around one year - then for some strange reason, picked up the wrong nozzle!? I wonder if it was because I was at a petrol station other than the one I usually use - I really don't know what happened - anyway, I put in 3.5 litres before realising my stupidity.

My tank was about 4/5 empty, so I immediatly changed over and continued filling with diesel, before driving home.

Straight away, I logged onto the internet and did a search - and there were so many conflicting recommendations. Hardly any of these were backed up with any experiences or hard facts.

So, since then, I have done about 2500 miles. I used pretty much the full tank of diesel before topping it up each time. I guess there are two schools of thought on whether you should continually top up, or use most of the fuel before topping up. I chose the second as by the time you put your second tank of clean diesel on top of the contaminated, you have diluted it to virtually nothing.

The first couple of tanks I nursed the car. Didn't go over about 1/4 throttle, didn't go over 65-70mph - just took it quietly, trying not to let things get too hot.

2500 miles on and it's still fine! Hopefully I haven't done any damage, but then the cars only worth �1000 - I thought it was worth the risk.

As an indication, my tank is about 65 litres, so:

Tank 1: 3.5/65= 5.4%, Tank 2: ~1%, Tank 3: <0.1%

Hope this helps anyone in a similar situation!

Danny Blair

1996 Renault RT-D 2.2 (non turbo)

I also put half a tank of petrol in my 06 Reg Audi A4 Diesel, drove it about 1/2 mile before the engine cut out completely. It was dark when I filled up and I was tired but I was dispensing fuel from a black hose that I always recognize as diesel. BAD MISTAKE.
I called recovery who wanted to tow me to my Audi dealer, I refused as I knew they would take me to the cleaners. Instead I chose a local garage with a good reputation who simply drained the fuel tank, replaced the fuel filter, flushed the system and all for �39.95 !!!! The car was fine after that.
No doubt if I had of taken it to the main dealer I would have been looking at hundreds of pounds.
Misfueling occurs 400 times a day in the UK. If it happens to you, don't drive the car, don't even turn the engine on! Get it drained out and flushed. Once done fill the tank FULL with the proper fuel. Some modern cars , when you use the electronic unlocking on your fob, PRIME the glow plug and pressurize the system. Try not to use the fob until the problem has bee sorted. It doesn't have to cost you a fortune (unless you take it to the main dealer).
I have just had the nasty experience of putting some petrol in my diesel engine here in Luxembourg. The car was taken to the Citro�n garage, the tank drained and refilled with diesel. The drainage cost was 40.88� + VAT uel-assist.html
these are the only people you need! they rock. dont tell your dealer or you'll lose your warrenty.
02 transit van 104000 miles on clock.
The red low fuel warning light had been on for last 6 miles,pulled into same garage i always use and put 30 quids worth in. 500 yds down road (kerput) van stopped dead and despite turning over would not start. Rang local garage who look after my van for a tow home, not possible,so rang wife. While i sat and waited i ran through all the possibilities why van wouldnt start, then it dawned on me, looking at till receipt from garage, what a plonker, �30 unleaded on top of possibly half gallon of diesel.
Towed home by wife, that was an experience,her first time towing and certainly my last being towed by her, no power steering and no brake servo on country roads 7 foot behind a chelsea tractor doing 60 miles an hour.
Next morning siphoned all fuel from tank, luckily no anti syphon on this model, so managed plastic tube and petrol cans, 7 gallon of mixed fuel. rang a couple of mates for advice, both been mechanics since leaving school, 30 odd years of experience each, What a pleasant surprise, not a problem they said,get some diesel in and turn it over till it fires, may be smokey and lumpy but it will clear.Worst case scenario would be to have to empty and clean fuel filter, could take as long as 5 minutes and cost you at least a fiver for a drink.Did as they said and it fired up 2 nd attempt,
lumpy for a few yards but other than that runs perfect.
According to my two mechanics,who both work at different garages and knew nothing of the others comments ,this is a regular problem but made worse by the cowboys who charge horrendous fees to pacify worried motorists. In the vast majority of cases once drained and refuelled proprly diesels will start and run with no long term effects.
if it is less than 25% of the capacity of your diseal tank, please do not worry. Just fill the diseal tank to full with diseal so that the petrol remains diluted. It will gradually get used. Keep filling up the tank with diseal & it will be alright. To get the petrol out, keep the cover of the tank open at night for one or two nights. The petrol will evaporate & your car will start running smoothly again. Since petrol is better fuel, no damage will occur if the concentration is low. IF you have more petrol than diseal, better empty the tank completely & fill up with diseal.
I had exactly the same problem,i filled my tank on my landcruiser to the top with petrol (its a diesel car!) at 2am 100 miles away from home in leeds!! what do i do now? fortunately when i went back into the filling station the man had seen this all too many times before and passed me a leaflet and told me to call them. the company was called Forecourt Assist and baring in mind its 2am i called.and within 20 mins a swish van pulled up and a very polite man drained all the fuel out of my car and cleaned out all the fuel lines etc and i was driving back home within an hour of making the call. their price was only �170 and am very gratefull for an amazing service that i dint know even existed. im not sure what areas they cover but i believe they do have a web site.
I had this same problem with my 03 Peugeot , I toped 17 litres of petrol on a quarter tank of diesel, and to be frank with you guys i did not realize this until driving from canary wharf where i bought this fuel in an unmanned service station, to lewisham, I noticed that my car was hard starting but does start that on the second try which was unusual, i still drove to brixton and left for home and that will be another 16miles to Kent (Orpington), on my way home i noticed my temperature was going on the high side i parked the car and raved the engine and then it dawned on me that something must b wrong cos my car was misfiring, I checked the receipt and wow it was unleaded petrol 17 litres. I didn't know what to do , but i decided to drive home cos i thought the damage if any must have being done , the next day i started the car took it to the garage and asked them to drain it out, and that was it, the car is fine and am fine , now i have like four stickers saying diesel all over my filling tank, the cost �40quid, I have to say i don't know why my engine did not go burst as i read in the Internet or my fuel pump and injectors, but i do believe it down to the fact that i had like 10 litres of diesel in my tank before topping up 17 litres of petrol, and luck i will say , my advice is if you ever have this problem, if you can park your car or take it to the nearest garage and have them drain it out and fill up with the right fuel , dont leave it too late cars are unpredictable God bless you guys
I've put diesel in to petrol tanks and petrol into diesel. It cost me £4 to remedy. It's called Petropatch. Clean a small area of the lowest corner of your tank, rubbing it with a bit of sandpaper back to the metal, drill a 5mm hole and drain your tank. Dry the surface, apply the Petropatch, refill your tank. Then spend £800 on a driving holiday to the south of France. (I did that)

So I managed to make the same mistake and read this page and was worried about the horror stories. I thought I'd let you know about my experience and how I resolved the situation....

I have a 2010 Vauxhall Insignia CDTI SRi (with a 100,000 mile / 10 year warranty) which uses a common rail fuel system and with around 5 -10 litres of diesel in the tank I put 24 litres of petrol in. I realised as soon as I put the pump back and didn't know what to do...
I then drove approx 1 mile (1.6km) home barely getting above 1000rpm (coasting where possible). Then I read this page and felt sick!
I tried syphoning the car from the fuel line entering the fuel pump without great success (modern cars have a gauze low down across the filler tube (where you put the nozzle when filling up) so I didn't even bother trying syphoning from the filler tube).

I found that the AA have a Fuel Assist service (
which deals solely with this issue.

Note that their main advice is, if you have put petrol in a diesel car and realised soon enough DO NOT START THE CAR.

I called the AA and the cost is £246 or £185 if you're a member. P.S. joining with the lowest grade membership was about £40 - so join.

The guy came out within an hour and knew exactly what he was doing. He asked if the Electronic Management light had come on at all (it hadn't) and whether the car was chugging at any point (it wasn't) and he said that there would be no damage and the car would be flushed clean once he was finished.

He then proceeded to disconnect the fuel line to the fuel pump and attached a hose from his van and pumped all the fuel out of the tank. He then put some kind of additive into the tank and also filled it with £12 of diesel (approx 8.5 litres). He advised that I go to the garage and fill the car full of diesel and once this got down to quarter full, to fill it again.

The only difference to the car at that point was that it took a couple of extra chugs to turn the engine over when starting the car. This had entirely gone after 1 day (50 miles driving).

£185 fee to drain the car (less £12 diesel and cost of additive)
£40(ish) fee for roadside assist AA membership
Damage to car NIL - although I should point out that this is probably because I had only driven a very short distance and I kept the revs very low. The engine management light did not come on and the car never chugged. I suspect the diesel never actually got into my engine, as there is a small reserve of fuel which sits in the fuel pump reservoir. As I mentioned earlier, the best advise I suppose, if you are aware of your mistake is DO NOT START THE CAR - CALL THE AA fuel assist programme on 0870 240 3985.

The guy said on no account should I tell the dealership because they would invalidate the warranty on the car, despite the fact that it was cleaned out and the electronic engine management system hadn't even detected a fuel issue. He also said that older diesel vehicles (those that don't use a common rail fuel system) could be topped up with diesel providing the petrol only amounted to 10% of the capacity of the engine. With vehicles using a common rail fuel system, it's better to get them cleaned out asap.

Trevor - if you're out there and read this - much respect and many thanks.

I have just come home, i have a 2010 Megane, my daughter put £15 worth of petrol in it, its a diesel.. I never realised until I got home and tried to start the car again. I have driven from Birmingham to Tamworth about 20 miles, it wasnt until I got on the motorway the car felt a little strange, I thought nothing of it, until I needed to go back out and it wouldnt start, I then rang my daughter an asked what fuel she put it,,,, then I realised she had put petrol in, I cant ring Renault as that will invalidate the warranty and probably be a hefty bill.... Help.... the car was driven and then I tried starting it 3 times when I got home..... have I damaged it.. more
Is it possible to put diesel in a petrol engine BMW M5 2006 model

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