Petrol in my diesel bakkie balls up

[Sean KZN]

[MJC]

I can tell you straight away that that is pure BS. As anyone who has accidentally gotten petrol into a diesel vehicle's tank will attest, it dramatically reduces the engine power. Generally a 5% petrol mix will suffer a 5% power loss. As the percentage gets higher, combustion starts to get erratic and the power loss is even more severe.

The reason why petrol does not work in a diesel engine has to do with the way it ignites and burns. Petrol generally needs a close to perfect fuel/air mixture to even burn consistently. The way a diesel injector injects the petrol into the combustion chamber does not lend itself to proper ignition and complete burning of the fuel, hence the very obvious power loss.

What you should never do, is get any petrol or petrol fumes into a diesel engine's intake system. This can cause pre-ignition and serious major engine component damage.

The damage cased by petrol in a diesel engine is caused by the lower lubricity of the mix. This causes friction and wear, especially to the high pressure (injector) pump. The injectors will likely be damaged much less, as the movement of the injector needle is extremely small compared to the pump parts.

I don't believe that petrol will damage any seals or pipes. Diesel fuel is generally harder on synthetic materials than petrol.

Using up to 15% petrol in diesel engines under extremely cold conditions is common practise. Bear in mind that the diesel tends to gel in these conditions, so adding the petrol merely restores it's viscosity (and likely lubricity) to the same point it was at more normal temperatures. Such a "winter" fuel mix may be a bad idea in very hot conditions, due to the lower lubricity of the mix. Adding a lubricant such as 2-stroke oil may be a good idea if you have some petrol contamination in your tank.

Interesting, thanks.

[MJC]

So I suppose there is no way of knowing if my vehicle is damaged?

It drives, but I am no mechanic and wouldn't know if there was concealed wear or damage.

[A-R]

So I suppose there is no way of knowing if my vehicle is damaged?

It drives, but I am no mechanic and wouldn't know if there was concealed wear or damage.

As I said, any damage will likely be in the form of accelerated wear, not sudden failure. So the service life of some components may have been shortened very slightly. Due to your immediate corrective actions, such damages should be minimal and not really measureable. Relax and enjoy your vehicle.

Just as an example: Our 1990 Hilux 2,4 Diesel (2L engine) was driven for about 20km with +/-75% petrol in the tank when still very new. It has now reached 600 000 km with the same injector pump and injector nozzles (and engine parts). The fuel system is indeed not quite the same as a modern common rail diesel system, but just an example.

[A-R]

Thanks, now I got the idea of the wax thing and the use of kerosene. There are lubricating additives in diesel oil, which pure kerosene does not have, so it makes sense to use kerosene as a dilutant.

The basic winter diesel we use here can be used to negative 30 degrees, but up in the north there's arctic version available with minimum temp of -40°C. Even if the winter/arctic diesel keeps it viscosity and can be pumped through the nozzles it's very hard to make ignite, hence the use of gasoline/petrol. Which does no harm to your diesel engine. Really.

About those Russian trucks: our army we used have them and it was said, that there could be a dozen Toyota Corollas following those trucks running with just the fumes of unburnt gasoline exiting the exhaust pipes of those trucks...

The lubrication in diesel fuel is not from additives, but from the heavier fractions left during the refining process. Okay, splitting hair, the nett effect is the same.

The difference in nomenclature here, in various parts of Europe, USA and Australia can be somewhat confusing. Kerosine may be a different thing in different parts of the world, just as the composition of diesel fuel differs according to refining method, raw material type and source (crude oil, coal, etc.) and intended use environment.

Then we have the European habit of supplying diesel fuel for automotive use and for heating purposes at different prices due to different tax loadings, and the efforts of the gubbermunt to keep people from using them for the "wrong" purpose to save money...

[MJC]

Thanks :)

[Johann du Toit]

It happened to me once. I did it to a rental bakkie in Cape Town. The Rental Car Agency was not happy but they quickly sent out a replacement vehicle (fortunately I didn't actually start the engine after realizing I filled up with the wrong fuel, so it would have been a simple matter of draining the fuel tank of all the petrol).