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Adding 71 liters of gasoline to a diesel engine

Benyamin Davodian
Hello everyone,

This message is for automotive or mechanical engineers only.

pay attention!!!

A customer claims that he accidentally put gasoline in place of a diesel in the Toyota LANCROZER 2008 model

The customer claims a vehicle traveled 14 km until he heard engine noises.

Questions:
  1. Is it possible that a vehicle can travel 14 km?

  • Will the engine work briefly and after a few meters stop?

  • Will the engine not work?

  • I would love to get feedback.


Thanks
  • 0
    Hello again, Benyamin. It is largely a case of how much wrong fuel goes in. With a very small amount you might get away with it. However you mention 71 litres in your post title. For a medium sized car that is about a tankful. The Toyota Land Cruiser is a large car and probably has a larger tank but 71 litres represents a sizeable portion nevertheless.


    Petrol is much more volatile than diesel fuel. Therefore it would detonate sooner in the compression cycle, possibly before top-dead-centre position, causing a reverse thrust.


    In answer to your questions:
    1. I very much doubt it. You would be lucky to travel 14 metres.

    • The engine could work until the petrol has had time to travel from the tank to the fuel management system. Then you would be unlikely to travel further.

    • It would not work properly. Any attempt to drive it would probably cause severe damage.


    If someone realises that they have filled their car with the wrong fuel, they should not even try to start the engine. Inside they should call the roadside rescue service, who will come and drain the fuel mixture out of the system and refill with the correct fuel.




  • 0
    Denis is wrong when he says that petrol would detonate sooner in the compression cycle as that is not where the problem lies. A petrol engine (spark ignition) uses the spark plug to ignite the fuel/air mixture at the correct part of the cycle, but a diesel engine (compression ignition) has a much higher compression so that the fuel ignites as it is injected. Therefore with the injection being at the correct point in the cycle (probably about 5 degrees before TDC) you will not have pre-ignition. The major problem is likely to be with the fuel injectors and pumps as they are designed for diesel fuel rather than petrol, and diesel has different characteristics.

    I have never looked into the effects of using petrol instead of diesel, but my guess would be that the fuel injection pumps and the injectors themselves would work after a fashion for a while before they give up the ghost, as the problem would be the petrol would not provide the designed lubrication of the moving parts. I suspect that the pumps and injectors would seize and need to be replaced if they have been used for any time. I am a bit surprised the car managed 14km, though perhaps the driver didn't notice funny noises to begin with. I certainly agree with Denis when he says "Any attempt to drive it would probably cause severe damage"!
  • 0
    Thanks. 

    I raised the issue because I wrote a legal opinion to my client. I recorded in my legal opinion that a vehicle could not travel much. And I'll explain. Already during engine start, noises and emissions of pollutants will start from the exhaust, so it can be understood that the damage is relatively small because the vehicle can not move. At the same time, the damage created is in the syringes due to grease dilution in diesel fuel during gasoline mixing and it mechanically causes damage to the syringes. Do you agree with me ?
  • 0
    I think you forgot about all the diesel already in the pipes between the fuel talk and the engine.


    The driver would have no trouble starting the vehicle and driving off.  How far they get is another matter.
  • 0
    There are direct injection petrol engines, and it is possible to modify diesel engines to run on lighter fuels, for example aviation spirit, many military vehicles are like this.

    It is actually very  common in cold countries to add a little petrol to the diesel to get things started in winter, but a small fraction,  perhaps 5% by volume.

    As others have noted, the diesel engine is lubricated by the fuel,and rapidly things will  wear.

    I'd be surprised at 14km, presumably half an hour or so, on pure petrol and not damaging the engine,  but if it was really a mixture with some diesel in the tank,  especially if the petrol sat on top of the heavier oil in the tank, and was not well mixed and not  burnt at first, perhaps.

    This rather silly video tries both petrol in a diesel car, and diesel in a petrol car, and certainly suggests the engines will run for quite a while in both cases, though the running is far from smooth, and there may well be significant  life reduction of the two cars.
  • 0
    The pump nozzles for diesel fuel are larger than those for petrol, so a diesel nozzle will not fit to be able to fill a petrol tank, but a petrol nozzle will be able to refuel a diesel vehicle (though it will be a rather loose fit so there are warning signs). The reason for this is that trying to run a petrol engine on diesel means the engine is damaged much more quickly - and probably more comprehensively (i.e. more chance of irreparable damage), while for a diesel engine running on petrol there is more chance of being able to recover the situation, or at least that is the received wisdom. As has been said previously, the problem with petrol in a diesel engine is the accelerated wear so it will continue to operate after a fashion while if it was the other way round I would expect poor fuel/air mixing, potentially incomplete combustion and potential damage to the spark plugs/valves and burning of the cylinder oil film causing lubrication problems (though my mechanical engineering days dealing with diesel engines are 35+ years in the past so this can't be considered an 'expert opinion' at this point).

    Direct injection petrol engines work differently from diesel injection, since for a petrol engine the fuel is injected in measured quantities but it is still the spark plug which causes the ignition, but for a diesel engine the air is compressed and then the fuel is injected at high pressure (the engines I dealt with were injecting at about 275 bar) so that the fuel is finely atomised and as the temperature of the compressed air is above the auto-ignition temperature of the fuel it immediately ignites. The pumps and injectors are designed to work with particular fuel characteristics (viscosity, etc.) so if the fuel is changed, this is where the modifications have to be made, and is presumably where the damage occurs when it goes wrong.

    The video on the link is interesting and many thanks for providing it, though it doesn't make me want to revise anything I have said previously, as the behaviour of the cars seems to be consistent with my understanding of where the problems are likely to be.
  • Former Community Member
    0 Former Community Member
    I think the OP said this was a landcruiser of 2008 vintage - so quite possible extensive use and reduction in compression on that particular engine. I'm with Mapj1 - chucking some petrol in for easier winter starting is common place, and many engines will run on a variety of fuels with some relatively minor adjustments


    Landcruisers are the vehicle of choice for every rag tag group operating at the edges of supply chain logistics and over the years I've seen them running in various parts of the world where fuel quality is in many cases questionable and supply is variable. It is often the vehicle into which you can chuck all sorts of concocted mixtures including palm oil, petrol, kerosene or 28 or 35 sec heating oil, DERV and in some places even TVO along with a pinch or splash of pain thinners, triclorethylene and pretty well any hydrocarbon group in between


    None of it meets manufacturer spec, and will probably void all sorts of warranties but a decent local guy used to tinkering with the injectors and pumps can often get them running on some unbelievable fuel mixtures - they often have their own local mixtures


    I think land cruisers have about 20 gallon tanks(European variants, US variants may be bigger to allow exploration of "The big country" - putting 15 gallons of lead free in, to fill it up mixing the petrol with about 5 gallons of diesel, might well allow it to run roughly and get half an hour or so use out of it   - although it won't have done it much good at all


    Regards


    OMS






  • 0
    Yes at that vintage it probably still had a mechanical injection pump. Most newer vehicles have had to move to common rail systems to meet the emmisions requirements. Mechanical injection systems will run on most things and 14km will only require a couple of litres of something reasonable. I guess they probably have large fuel filters to deal with dubious fuel quality which will give a reservoir of good diesel..

    As the petrol proportion increased it would almost certainly knock badly but after a clean out and fresh diesel I expect it will still run.

    If it's a newer variant with common rail injection there is a greater risk of injection system damage due to the recirculation of the fuel.


    Best regards


    Roger
  • 0
    Alasdair Anderson:

    Denis is wrong when he says that petrol would detonate sooner in the compression cycle as that is not where the problem lies. A petrol engine (spark ignition) uses the spark plug to ignite the fuel/air mixture at the correct part of the cycle, but a diesel engine (compression ignition) has a much higher compression so that the fuel ignites as it is injected. Therefore with the injection being at the correct point in the cycle (probably about 5 degrees before TDC) you will not have pre-ignition. The major problem is likely to be with the fuel injectors and pumps as they are designed for diesel fuel rather than petrol, and diesel has different characteristics.

    . . .


    Hello, Alasdair. Evidently on this occasion I did not make myself sufficiently clear and was a little too casual in my choice of terms. I should not have used the word "detonate", and I am sorry for the confusion this has caused.


    I am well aware, of course, that a diesel engine has no spark plugs and the fuel ignites following injection near TDC. I do maintain that the different combustion characteristics of petrol change the nature of the combustion sequence, and this has an adverse effect as well as the deleterious effect of the non-lubricating qualities of petrol.


    Much information on the Internet, particularly from breakdown rescue services, focuses on the lack of lubrication quality of petrol, possibly because it is easier to explain, and of course I do not deny this is a major part of the issue. I have found some further interesting articles, which describe the much-faster rate of combustion of petrol within the cylinder.

    http://www.differencebetween.info/difference-between-petrol-engine-and-diesel-engine
    https://me-mechanicalengineering.com/comparison-between-petrol-and-diesel-engines/


    In the diesel engine most of the combustion takes place in the power stroke as the volume expands, whereas in the petrol engine combustion takes place in a shorter period of time at the top of the stroke. In thermodynamic terms, diesel engines are based around the Diesel cycle and petrol engines around the Otto cycle. A diesel-petrol mixture would have characteristics approaching that of petrol so combustion would take place too rapidly for the design of the diesel engine, especially in view of its slower rotation, causing impacting forces that it is not designed to take.


    Thank you for agreeing with me on the point of attempting to drive would cause severe damage. It seems that the Land Cruiser described was a tough old beast, and it is amazing it managed 14 km! ?


  • 0
    Good morning,

    As an understanding and in the automotive field for many years I can say with certainty that an engine as I posed in my question while introducing gasoline into a diesel engine can not travel much and will explain: Already at the start of the engine will make noises and power loss, emission of pollutants in the exhaust, so there is no slim chance that the vehicle can travel Much.

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