How far will a car drive with wrong fuel? 2

This is a question allot of people ask if they are unsure of whether or not they have put the wrong fuel in the car.

The answer differs greatly, some cars die before they leave the forecourt, some can drive for 200 miles or even more but refuse to start again from cold, it is best answered by giving you the facts and you can work it out yourself

1) when you misfuel the percentage of wrong fuel matters, the more wrong fuel generally the early the engine refuses to run

2) there is between 500ml and a litre of fuel in the filters and pumps, after misfuelling when you start the engine it will be running on the clean fuel in the system that you had when you arrived at the pump, this can take between 10 seconds and 10 minutes to effect the engine

3) on an already hot engine many diesel cars will drive (albeit rough) with petrol in them, the problem starts when the car is left overnight and refuses to start in the morning, flat batterys after a misfuel is a common occurance from people trying to start the car not knowing they have misfueld.

4) the type of engine matters, sophisticated highly tuned diesel’s are more sensitive to fuelling issues, the sporty volkswagon diesels in particular – but they recover fine after a fuel drain

5) driving at a steady speed with misfuel will get you further than stop start traffic, this is not always the case but what i have seen suggests it

6) taking any chances is not worth the risk, if you misfueld would you rather get your car drained down on a well lit petrol station forecourt with ample supplies of coffee and cake whilst you wait 45 minutes for a fuel drainer to arrive – and be on the road in 30 minutes after he arrives , or take the chance of sitting by the side of the road broken down at neither a place or time of your choosing whilst waiting for a recovery vehicle?

7) If you have any doubt you have misfueld or put petrol in your diesel its well worth carrying out an olfactory test, go on have a sniff! if your diesel tank smells like petrol – even just a wincy bit then it is

hope that helps

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2 thoughts on “How far will a car drive with wrong fuel?

  • gordon barclay

    hi.i run a 2.8 pajero on a mixture of diesel and used veg oil have done for about 5 years or so.I have seen in forums that they add a little petrol to it in the winter months to help stop the fuel getting thick with the this ok to do.thanks.gordon.

    • TheFuelMan Post author

      Hi Gordon,

      Ive heard off this as well and its popular in Siberia in the winter where the diesel fuel available has not been treated with additives.

      The only reason to put petrol in diesel is to stop it waxing, this happens at about -20 (which is why its done in siberia). diesel starts to cloud at -9.5 and get thicker until it freezes into a waxy lump at -20

      The fuel we have in the UK has an antifreeze agent put in from October through February which is good to about -15

      Petrol is bad news in any modern diesel, it destroys rubber seals, diesel hoses, plastic fuel tanks and also pressurizes the fuel tank (diesel doesnt vapourize – petrol does), there is also an added (but not likely) fire risk due to the differences in fuel systems as diesel is a stable fuel and petrol is a volatile fuel which vapourises, diesel hoses, fuel lines and pumps are all diesel specific.

      As for performance in the cold if anything it reduces it because of petrols ability to non combust under compression – exactly the opposite of diesel.

      Hope that helps