Unleaded petrol for diesel engine

[lwlwoo]

I accidentally lifted the wrong nozzle and put in about 1.24 litre of unleaded petrol into my E320 Cdi fuel tank. Because I filled up the tank right up to the rim at the end, there should be about 16 gallons (72.8 litres) of fuel as a whole. Quick calculation will show that the contamination is about 1.7% of unleaded petrol. Does anyone know if this will damage the 320 common rail diesel engine. A moment of day dreaming has led to this silly outcome.

FPM

 

[Bolide]

Petrol in diesel engine

Quick answer: read the owners manual

In my old 250TD the manual gives the percentage of diesel you can put in a petrol car and vice versa. Your car uses a completely different engine so I'd expect its tolerance to petrol to be low. I'd advise not starting it!

There was a long piece about this in the Telegraph last week. You can look it up online. Average costs incurred are, they reckon, £4k +


Nick Froome
www.w124.co.uk

 

[mlc]

I worked for the AA for a number of years, but left about 7 yeras ago. At that time the rule was upto 10% of the wrong fuel was ok. I cant believe that under 2% of petrol could do any damage, however it is worth taking advise from you motoring organisation. If you ask MB I am sure they will tell you it needs to come out at great expense, but they would say that wouldnt they!

Mark.

 

[Rory]

I put just 7p (thank God) worth of unleaded in my C270 just after I got it (6mths ago) so read up quite a bit on the subject (in case I did it again).
On older engines it's really not an issue - tales abound of people running at 50/50. On newer cars it's more of an issue, but the concensus (of internet forum posters, not professional opinion) seems to be that you'd probably get away with 10%.

1.7% seems hardly measureable. For belt and braces you might want to add some Millers Diesel Power Plus to provide extra lube for the fuel pump. The main thing I'd do is keep topping it up to increase the dilution and use one of the 'super' diesels that's a few pence dearer than the ordinary stuff, or one that's part bio diesel.

Oh, and don't tell MB, particularly if the cars under w'tee.

As I also still own a petrol car I've got into the habit now of starting to fill, then immediatley stopping and rechecking all's correct.

 

[lwlwoo]

Thanks for all the advice.

I managed to find the Telegraph article that Bolide has referred to after a Google search. It didn't say how much unleaded petrol those unfortunately drivers had put in by mistake during their diesel fill-up. I reckon that the amount was substantial in all cases that mentioned.

I rang MobiloLife this evening (should have waited for Rory's reply first but my car is 5 yrs old and so it is out of warranty). As expected, they said the car should not be used at all. It has to be recovered to the nearest dealership for repair. As we all know, this will mean a very hefty bill.

For this reason and because of the low level of contamination, I decided to risk it and keep running the car. I did about 20 miles first and then topped up with more diesel (3.75 litres). After this, I did another 85 miles and then again filled up with fresh diesel (8.55 litres). Here, as already suggested by Rory just now, I have been trying to dilute the contamination and I reckon that the level of petrol is now at around 1.4%, down by about 0.3%.

What I can say after driving 105 miles so far is that the engine still seems OK. Any potential damage perhaps will not be noticeable at this stage but I hope by keep bringing down the level of petrol from now on I can get away with any significant damage to the engine. After hearing the latest advice, I shall also consider adding extra lubricant to the tank.

I know only time will tell!!

FPM

 

[davidsl500]

interestingly in the "old" days a gallon of petrol was often added to a tankful of diesel to stop it freezing in the midst of winter time. Of course that was on older style less sophisticated engines...

It occurs to me that the specific gravity of diesel and petrol are different. I would presume that the petrol would be lighter and thus would "float" on the top of the diesel? If the petrol and diesel dont actually stay "mixed" then it stands to reason that if you left the car standing for maybe a day then you could syphon off the top couple of gallons carefully and see if it seperates out.

This assumes that the petrol is the "lighter" liquid of the two and that petrol and diesel doesnt combine and stay combined. If it seperates out you could measure the petrol content and see if your engine had actually consumed any petrol at all! Just a thought....

 

[paulcallender]

If you can manage to separate out all the constituents of petrol and diesel simply by leaving them in a tank, please tell Shell and all the other refinaries how its done! They spend huge sums of money building fractional distillation plants to do this job!

 

[PRS]

I do not believe that the small amount of petrol you put in relative to the full tank will do any damage at all, and as for it sitting on the top of the diesel, you will have to brake very carefully and go round corners very slowly.

 

[lwlwoo]

Hi,

Correct me if I am wrong. Both diesel and petrol are hydrocarbons. Although they have different densities and vapour pressures, they are indeed miscible. Hence, I reckon the petrol contaminant will be dispersed and diluted when the car is in motion over bumps and through corners. Need a petroleum chemist to enlighten us. Thanks!

FPM

 

[paulcallender]

Hi,

Correct me if I am wrong. Both diesel and petrol are hydrocarbons. Although they have different densities and vapour pressures, they are indeed miscible. Hence, I reckon the petrol contaminant will be dispersed and diluted when the car is in motion over bumps and through corners. Need a petroleum chemist to enlighten us. Thanks!

FPM

100% correct! You were obviously listening in your O-level/GCSE chemistry lessons!

 

[rallen]

I would have assumed that the difference between various diesels around the pumps amounts to more than 2%. I cannot see why petrol stations never make mistakes when they fill up their storage tanks or that the tanks are not full of rust, water, parafin etc

 

[davidsl500]

If you can manage to separate out all the constituents of petrol and diesel simply by leaving them in a tank, please tell Shell and all the other refinaries how its done! They spend huge sums of money building fractional distillation plants to do this job!

Nope, they spend huge amounts of money extracting the products from raw crude oil which is an entirely different process. To do this they use lots of heat, cracking agents, catalysts etc., to "unlock" and seperate the products. If you took all the products distilled out and simply added them all back together and shook them up a bit you wouldnt get crude oil back again !

As for PRS 's commenting that the petrol would be sitting on top of the diesel - I never suggested it would ! I suggested that if you left the vehicle stationery for a day (maybe longer) then maybe the petrol would seperate out and sit on top.I know its going to be mixed up with the diesel when driving around, thats pretty obvious.

The question posed was "would the petrol seperate out?" and no one has yet given a conclusive answer to that. Of course I could go out and buy half a gallon of each, mix em up and see what happens - but i couldnt get a mortgage.......

 

[nicky]

If you mix petrol and diesel, it will stay mixed......I have seen the contents of a tank that has been removed after mixing and it stayes as one.....So david no need to go out and experiment......

 

[paulcallender]

Nope, they spend huge amounts of money extracting the products from raw crude oil which is an entirely different process. To do this they use lots of heat, cracking agents, catalysts etc., to "unlock" and seperate the products. If you took all the products distilled out and simply added them all back together and shook them up a bit you wouldnt get crude oil back again !

As for PRS 's commenting that the petrol would be sitting on top of the diesel - I never suggested it would ! I suggested that if you left the vehicle stationery for a day (maybe longer) then maybe the petrol would seperate out and sit on top.I know its going to be mixed up with the diesel when driving around, thats pretty obvious.

The question posed was "would the petrol seperate out?" and no one has yet given a conclusive answer to that. Of course I could go out and buy half a gallon of each, mix em up and see what happens - but i couldnt get a mortgage.......

I have a degree in Chemical Engineering. I'll try and make this as simple as possible:

Fractional distillation works by heating the crude oil and allowing it to cool, on many trays arranged vertically. The tower is hottest at the bottom and coolest at the top. So, you draw off (as a liquid) the lighter ends from the top and the heavier ends from the bottom. Petrol is approximately C5-C10 and diesel is around C12 and higher.

Cat cracking is a different process, where the larger chains of alkane and alkene, are split into smaller chains. This is done, simply becuase the fractional distillation process produces too much diesel and too little petrol, for market demand.

By the way, if you add a catalyst into the process, you don't end up with catalyst (except tiny trace amounts) in the product you are making. If you did, then its not a catalyst, its one of the raw materials.

If you mix petrol and diesel together, they will not separate, no matter how long they are left. If they do, I will eat my own foot. I am that confident in it!

If you still don't believe me, look at this: http://www.citycollegiate.com/petroleum_IX.htm

 

[davidsl500]

Bugger !, So no chance of calling you Mr Hoppy From now on Paul !...

So my next suggestion of lighting a large fire under his diesel tank to re-distill the petrol out is probably not going to go down to well either.......

I should think that lwlwoo is probably half way down his tank of fuel anyway by now and i would think that diluting the contamination with fresh diesel top ups is probably the most sensible way - short of draining and cleaning the tank to lessen the impact further.

Of course you could always sell the car to an unsuspecting BMW owner...

 

[lwlwoo]

Just to update you guys the engine is still running fine. The level of contamination has now come down to ca. 1.2%, down by 0.5% from the original level, after about three tops-up and ca. 165 miles of driving. I have also added an appropriate amount of Millers diesel power plus to the tank in an attempt to improve fuel lubrication, as advised by Brolide. My feeling from all your wise advice so far is that the negative effect on the cdi engine perhaps has been minimal. I shall carry on doing the top-ups for a few more times by then I reckon I'll finish the tank up in one-go before re-filling again. That said, the current threats of fuel shortage will encourage me to do top-ups for a while!

FPM

PS. I have a higher degree related to Chemistry and so my chemical knowledge is beyond A-level. However, I have been communicating with a few experts here and so all your advice has been very helpful. Thanks again!

 

[Ntha]

Hi,

Correct me if I am wrong. Both diesel and petrol are hydrocarbons. Although they have different densities and vapour pressures, they are indeed miscible. Hence, I reckon the petrol contaminant will be dispersed and diluted when the car is in motion over bumps and through corners. Need a petroleum chemist to enlighten us. Thanks!

FPM

Not a petrochemist, but a chemist. Absolutely correct. As the previous responder said, otherwise there would be no need for refineries, would there? Mind you, by the same argument, you can leave it in open trays and the petrol will preferrantially evaporate, but then again just as likely will start fire.

 

[blassberg]

seems we have an increasing number of company car drivers at our place choosing diesels and sometimes they, but sometimes their relatives / friends are filling up with unleaded.

Advice is to warn other drivers of your diesel vehicle and consider purchasing a dieselguard.... see http://dieselguard.com/

 

[JPM993]

Hello,

I put in about 12.00 into my diesel C Coupe about 12 months ago, drove it around for another 9 months, put on about 15K miles and not a problem.

I just keep topping up after about 1/3 of a tank had been used to try and 'dilute' it for 10 fill ups.

You'll be fine.

 

[paulcallender]

I accidentally put some unleaded petrol into my lawnmower. It caught fire and never worked properly since. Mind you, it was an electric Flymo...