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Wrong fuel, petrol in a diesel

Discussion in 'Engine, Drivetrain, Fuel and Exhaust' started by DIYMAN, Sep 8, 2018.

  1. DIYMAN

    DIYMAN Senior Member

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    Your Mercedes:
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    Something I thought I would never do, I put 22L of petrol in my E270 before realizing my mistake, I then filled to the brim with 55L of diesel. The tank was about a quarter full before starting so I think the total mixture in the tank is about 1/3 petrol 2/3 diesel, I drove home about 20 miles without any apparent problems.
    I know the petrol will degrade the lubricating properties of the diesel, so I was thinking that rather than have the tank drained could I just put 5L of engine oil in the fuel tank to compensate.
     
  2. EmilysDad

    EmilysDad Senior Member

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    I doubt it could be that simple .... :confused:
     
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  3. Jkh112

    Jkh112 Senior Member

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    I agree. Although if you were going to add some oil for lubrication then I would have thought 2 stroke oil would be better than engine oil.
     
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  4. om613

    om613 Senior Member

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    OOOh, that ratio would have me a bit worried...

    But fear not. Add 5L of KTC or whatever veg. oil - and just forget this misdemeanor.
    Adding mineral oil is not the way to go here...
     
  5. LostKiwi

    LostKiwi Senior Member

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    Personally I'd want to drop the petrol percentage down to less than 10% to ensure lubrication of expensive high pressure components.
     
  6. Xtractorfan

    Xtractorfan Senior Member

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    Add 2 stroke oil only, about 1/2L-1 Lt should be enough. 2 stroke oil won't do any harm. VEG oil will ruin your seals and will probably congeal in the system so don't add it.
    Engine oil is ok if you don't have 2 stroke.
    You may have to change the fuel filter if the car gets hard to start or it runs badly.
    Drive it as much as you can, and it should be ok.
    If it is driving ok, fill up again with diesel as soon as it drops in the tank.
    If running badly get it drained and change the fuel filter.
    You may be covered by your insurance or if you belong to any of the motoring organisations. So check it out.
     
    Last edited: Sep 8, 2018
  7. John Laidlaw

    John Laidlaw Senior Member

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    Personally I’d get the tank drained and start again, ain’t worth it- ratio is too high
     
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  8. Frontstep

    Frontstep Senior Member

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    I suppose the ratio of petrol to diesel has reached a level where the flash point has been significantly affected (lowered) as well as the lubricity, I am not a chemist so I don't know the points at which problems occur .
    Saying that I would put some 2 stroke in if it was mine.
     
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  9. Neil C1

    Neil C1 Active Member

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    Done this before once and was advised a small amount of 2 strike oil will be the best way. Can’t remember the ratio I was told but it must be about 50:1 max. Then top up every 100 miles for a few Weeks then full tank diesel and redex. I’ve never had a problem since
     
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  10. AJD

    AJD Senior Member

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    Don't take any chances. I did the same thing when I had a diesel. I just called the AA who drained the fuel system. The charge they made was £220 which was well worth it. OK it cost me a morning and we didn't get to where we were going that day but it alleviated any worries we might have had. :rolleyes:
     
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  11. thebiglad

    thebiglad Senior Member

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    Every time you use the car, cram in more diesel and the ratio petrol:diesel will move in your favour.
     
  12. mioba

    mioba Senior Member

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    hmmm bit of a tough one this, if the ca seems to be running fine and you happy then I would keep topping up with diesel.

    If you have AA or RAC and want to fork out if your worried then go that route.

    A houses for courses scenario if you ask me.

    If it was me I would drain out myself and get fresh diesel in. not sure how much potential damage that petrol could be doing.

    good luck and let us know how you get on
     
  13. OP
    DIYMAN

    DIYMAN Senior Member

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    Just an update for now, I lost my nerve and decided to get the tank drained.
    The technician is due here in about an hour the cost £165 including £10 of new fuel, so together with the £100 wasted in the tank total cost so far £265.
     
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  14. John Laidlaw

    John Laidlaw Senior Member

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    Can’t blame you, for what it’s worth I think you’re right to do it
     
  15. OP
    DIYMAN

    DIYMAN Senior Member

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    Next update, he has just left having removed 84L of fuel so the mixture was 25% petrol 75% diesel.
    He pumped the fuel out through the filler pipe and I was surprised to see he ran the engine the whole time, he said this was because it is a saddle tank and the fuel pump is needed to equalize the two halves.

    Thanks for all the suggestions on here to date, I am just hoping I will not have anything more to report on my stupid mistake.
     
  16. Jim2

    Jim2 Senior Member

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    I would always shake my head in wonder at how could anyone make a mistake like putting petrol into a tank of diesel ( or vice versa) until I did it myself...:shock: as luck would have it, engine failed about 200 Mtrs from my own house ( but had to cross a busy road to make a turn ) Luckily, I made it in free-wheeling mode, and got safely parked at the house. ( That in itself was an achievement.. give the volume of traffic on the road ) So next morning, disconnected the feed pipe from the filter, and switched the ignition on ( was an Audi A6 TDI) tank drained itself, so put 20 ltrs fresh diesel into the tank, connected the pipes back up, and after a bit of turning, the engine started. But lesson learned...…:D ( I hope...……o_O) For relatively small amounts ( 5-10 Ltrs) I would drive-top-up-drive-top-up etc. and I think that it would be fine. It's all down to the %. Petrol to Diesel. I think that it happens to many drivers, over the course of their driving careers. Anyone here on the forum NEVER had it happen to them? :)
     
  17. EmilysDad

    EmilysDad Senior Member

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    The only time I mis-fueled was with an Astra (not common rail) that was virtually empty and I put £10's worth of petrol in it. Amazingly it drove the few miles home with no problems at all. The next morning however it wouldn't start. I used my Pela to suck out the gallon & half of mostly petrol, re-filled with diseasal & away it went ... eventually.
    It seems that they altered the size of the wrong fuel nozzle all those years ago :)

    This is interesting though old tech diesel
     
  18. Wighty

    Wighty Senior Member

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    I know its done and paid for now, but something like a Pela mentioned above , could that be just inserted into the fuel tank and used to suck out the fuel ?
     
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  19. alexanderfoti

    alexanderfoti MBO Forum Supporter Authorised Forum Supporter

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    You could, but for 84L it would take a while!
     
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  20. Wighty

    Wighty Senior Member

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    It could take 2 days to save £200 :D
     
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