Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell?

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Sat 28 May 2011 21:03
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - macru

Is it possible to tell if a previous owner of a car has mistakenly refuelled a car (in this case a Mercedes) with petrol instead of diesel?

If they have, are there any symptoms in the car's behaviour that might show eg reduced fuel consumption?

Appreciate your thoughts

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Sat 28 May 2011 21:14
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - unthrottled

No, there isn't. Alas.

About all you can do is take the car for a run and when you get back switch the engine off. Then try to restart it. This should be easy for a diesel in good condition. If it struggles with a hot start, it could be a sign of a worn High Pressure fuel pump. The test can throw up false positives, however. There are other, far less expensive problems that could cause the same problem.

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Sun 29 May 2011 23:07
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - macru

Thanks, appreciate your comments.

Have just put a deposit on the car, but was a bit spooked by someone's suggestion that it may have been misfuelled. No concrete evidence 'tho.

Will try the restart on a hot engine when I next take it out and cross fingers everyrthing's ok with it.

Thanks again

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Sun 29 May 2011 23:19
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - unthrottled

Yes it is a concern, but one that has possibly been overblown. There is a school of thought that suggests that even one misfuelling incident will lead to inevitable HP pump failure. I think that this is an exaggeration.

That said, if I had a good diesel that wasn't broken, I wouldn't change it unless I had to. The ubiquitous VW 1.9 PD engine is about as efficient as a small diesel engine ever will be (best BSFC of ~200g/KWhr), and subsequent engines will never beat it by a large margin-whatever the magazine adverts say! There's a lot to be said for the comfort of knowing how a car has been treated.

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Mon 30 May 2011 00:32
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - bathtub tom

I bought a 3-year old Focus that needed a new pump after a couple of years of ownership (£1200) and sub 50K miles. It was suggested it may have been mis-fuelled at some time in its life to account for the early failure, although no-one could produce evidence.

I loved driving it, but couldn't justify the risk of further expensive repairs and gave up diesels.

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Mon 30 May 2011 08:49
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - Armitage Shanks {p}

I managed to mis-fuel a diesel. I stopped refuelling, brimmed up with diesel and and added a triple dose of Millers diesel Plus. The car is still running fine after 50K miles in 5 years. The outcome can be disasterous but not very often, as unthrottled has suggested.

I beleieve it is possible to do an analysis of the fuel in the tank, at a huge cost. If there has ever been any petrol in a diesel tank it should be possible to detect the 1 part in a million residue but what would it cost?

Edited by Armitage Shanks {p} on 30/05/2011 at 08:51

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Mon 30 May 2011 13:01
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - unthrottled

But by the time you got the results back, the car would probably have gone...

Thinking about it, petrol and diesel are miscible and there is some overlap in the weights of the components of petrol and diesel. So you can't really test for 1ppm like you can with a trace dye.

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Mon 30 May 2011 15:31
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - Dwight Van Driver

I am like AS above. Did a small amount of petrol into tank that I keep nearly full and well doused with Millers Additive. No problems.

Do not MB keep a computor record of work carried out on their vehicles. Maybe a misfuel would show up?

dvd

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Mon 30 May 2011 16:12
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - unthrottled

Maybe a misfuel would show up?

Only if you phoned them up and told them what had happened! Detecting petrol that WAS in the tank is the equivalent of a TV detector van that can 'tell' if you're watching television...

Edited by unthrottled on 30/05/2011 at 16:14

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Mon 30 May 2011 18:45
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - macru

Interesting comments.....thanks

Will keep Millers Plus in mind for any future mishaps - I hadn't come across that before

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Tue 31 May 2011 10:00
Mercedes-Benz E-Class Estate - Petrol in a diesel engine- is it possible to tell? - Bobbin Threadbare

You get thick white smoke if diesel is contaminated. You could drain the tank and fill it to the brim with diesel. You can get some goo that helps to clean it too (redex?)

I think the panic about misfuelling is over-egged somewhat - people must do this all the time! Replacing the fuel filter is a possible solution after the tank is drained I guess.

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