Petrol/Diesel Mixture

[alanporter]

On a different forum I saw recently, the writer stated that he always added five percent petrol to his diesel fuel, to aid a difficult starting problem. I am not an engineer but this seems to me to be an unwise practice. Could any engine wizards out there comment on this ?

<hr width=100% size=1>Alan Porter

 

[duncan]

other advice has stated (1) they don't mix, and (2) a friend's blew a head gasket diagnosed as resulting from too much petrol left in the tank after a re-engining excercise.

I agree doesn't seem sensible and I don't understand why petrol would aid a starting problem - it needs a spark which is (or should be) in short supply in a diesel engine!

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[philip_stevens]

I inadvertantly tipped 5 ltrs of outboard mix, in with about 20 ltrs of diesel. The outcome of this mistake was that the fuel gassed up quite often, resulting in the engine stopping frequently.

I managed to make port under stop/start engine power, and then had to drain all fuel from the tank, get it ashore for disposal (the local Alderney airport fire service used it for practice), and then refuel with clean diesel.

At this stage, all started to operate correctly again.

I learned to use different coloured containers, as well as reading what I had written on the containers - diesel or outboard mixture!!


<hr width=100% size=1>regards,
Philip

 

[Freebee]

This is what some misguided souls do to try and get easier starting in winter instead of buying winter grade diesel its not a recommended practice

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[spanners]

I agree with Duncan ,,
seems a dangerous practice ,, if you ask me ,,


<hr width=100% size=1>Tis meself, so it is.

 

[snowleopard]

a friend who runs a road tanker fleet tells me that diesels will run ok on up to 20% petrol. if you put more than that you lose lubrication in the injection system.



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[stubate]

1: diesels will burn anything that is oily/combustible
2: however, it has to pass thru the injection system and that is when the probs start. the fuel has to lubricate and cool the finely machined parts, that is why the plonkers in south wales using cooking oil in their cars will come to a "sticky" end.
3: the timing or firing point, just as in a petrol engine, is set to whatever fuels are to be used, petrol has a higher "exploding" point than diesel and will detonate in a diesel engine causing a pinking effect, that is why when you inadvertently fill your diesel car up with petrol it starts running "rough",
the advice to put a bit of petrol in your diesel in the winter is to make it easier to ignite.
the lighter the fraction the easier it is to ignite, that is the principal of the choke in a petrol engine, you richen the mixture so that you get more light ends that are easier to ignite, if you put a bit of petrol in the diesel it will have the same effect. however if your engine needs a starting aid such as this then it is probably shagged anyway. however i can see a use in diesel that has stood exposed to air and where some of the lighter ends have evaporated.
stu

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[vyv_cox]

I understood that the only reason for adding a small amount of petrol to diesel was to dissolve the wax that will block the filter at temperatures below about -5C. It has only happened to me once but the vehicle was virtually undriveable. I put half a gallon, the smallest amount I could buy, in 12 gallons of diesel. Fixed it instantly.

In UK these temperatures occur so rarely that this is probably a valid treatment, except perhaps in the Highlands of Scotland. I knew a truck operator who always put a couple of pints per tank in his trucks in winter. Never seemed to do any harm.

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[johnsomerhausen]

When Willy de Roos (of "Williwaw", the first yacht to make the Northwest passage from the Atlantic to the Pacific) went to Antarctica in 1983, he enquired from Ford (for his engine) and Petters (for his generator) what kind of fuel to use for the cold conditions there, both firms said to use kerosene (paraffin) with the addition of SAE 30 lubricating oil (Petters said betweeen 3 and 5%, Ford said 4 %). Some people have since suggested using outboard engine oil. I haven't heard any reports on the efficiency of that mix, but Willy told me the kerosene/oil mix worked perfectly.
john

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[andy_wilson]

Spark?

Petrol, like any fuel needs to reach it's flash point to ignite, something that occurs in any spark ingnition engine that is pinking - just before the spark sparks.

In a diesel engine the heat of compression would ignite neat petrol about 1/2 way up the compression stroke.

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[stubate]

so the petrol magically

permeated through the pipe work to the wax blockage and melted it away, gosh golly, and that was after it was diluted by all that diesel.
i must remember that.

stu


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[jimi]

My father was a quarry manager in Scotland, amongst others there were two things he insisted on the machinery operators doing.
1) never having a tank less than half full
2) Addition of a small amount of petrol to the diesel in the winter.



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[vyv_cox]

Re: so the petrol magically

Well, pretty much, yes. Within a mile the engine ran fine, after 15 miles or so of very intermittent progress.

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[stubate]

compression ignition, says it all doesnt it,

when you compress air and fuel enough it goes bang,

whether it be gas, diesel, butter, coconut oil or petrol, IT DOESNT NEED A SPARK !!

Stu

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[stubate]

Re: so the petrol magically

but you said the fuel filter was blocked with wax? if that was true the engne wouldnt run!!
stu

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[jmp]

Looked with interest at the responses .

Just aquired 10gals of kerosine (white paraffin) from a recently aquainted chap.

He told me they had loads,and it costs £1 a gal. He adds it to diesel in vehicles they are exporting to Russia to prevent it from waxing.
Don't know about starting however.

<hr width=100% size=1>jmp

 

[PeteMcK]

Long distance truckers

in the US used to mix in up to 25% petrol when travelling from the warm south to north in winter. Presumably the fuel supplied in the south had no anti-wax additives or treatment. My experience with diesels 20 years ago was that the Scottish climate would cause waxing (and complete shutdown a couple of minutes after starting) 4 or 5 days every winter; using 10% petrol in the winter removed the problem. You're forecourt diesel supplies are now "winterised". As for damage to the pump, etc., we have the luxury of a tight spec on fuel in this country but, elsewhere, I've seen liquids sold as "diesel fuel" ranging from something like machine oil all the way to, literally, wide-cut kerosene jet fuel. Older designs were meant to cope with this.

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[PeteMcK]

Would - if that\'s how it worked

But it ain't.

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[stubate]

well how does it \"work \" then

?

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[stubate]

why bother with paraffin?

when red diesel is about the same price and is set up for the vagaries of our weather,
plus you would have to add 30sae oil for the lube factor.



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