Little bit of petrol in a diesel tank?

cormie

Howdy,
Not that I've done it, but I heard that if you put maybe 3-5 litres of petrol in a full tank of diesel every once in a while, that's it's actually good for the engine. Is this true?

peasant

It never was good for the engine, but before there was "winter diesel", people had to put some petrol into their tanks in cold climates to prevent the diesel from becoming more or less solid in the cold.

joolsveer

I recently put three litres of petrol in my van tank by accident and it hasn't killed the engine. I won't want to make that mistake again. I was worried that the engine would seize up as I had heard a lot of dramatic stories of metal meeting metal without the lubrication of diesel.

Ferris

I've heard that if you put say half a tank of petrol in a diesel car by mistake what you do is put a pint of two stroke oil in with it and fill the rest with diesel. Mind you the guy who did it was driving a Hiace. Anyone else ever heard of this?

skyhighflyer

In my petroleum injection technician days the local mechanic we called would often opine that 1/4 tank of petrol in a diesel was OK. However, apparently the most he'd go with modern diesels would be a gallon in a full tank.

peasant

Leaving aside all the lubrication issues affecting modern injection pumps etc, you do not want mix petrol and diesel.

Both fuels have very different flashpoints and ignition properties. Best case scenario your engine would run and sound like a bag of nuts(or not at all) worst case you'll actually physically break something.

Ferris

With petrols lower flashpoint would you'd get some detonation (combustion mix ignites before the piston reaches TDC). This is not good for any engine and would damage crank, conrods, pistons and big ends in time.

Fey!

I remember my mechanic adding a gallon of petrol to a tank of diesel to bring the emmissions down before an NCT. That was on his sister-in-laws Nissan Sunny (or was it a Toyota Starlet?).

cormie

Fey! wrote: »

I remember my mechanic adding a gallon of petrol to a tank of diesel to bring the emmissions down before an NCT. That was on his sister-in-laws Nissan Sunny (or was it a Toyota Starlet?).

Think that was the reason I was given aswell. Something about it being good for the black smoke that comes out when the revs go up..

Run_to_da_hills

If you are using a common rail fuel pump as in most diesels these days, your pump could be knackered 20 miles down the road with petrol contamination causing thousands of euros worth of damage. It is worth draining everything and replacing filters etc.

Esel

Cormie, this is one idea that will not save you money!

You can buy a ton of monkey nuts, crush them, filter the oil and use that. Don't know if it will cure black smoke though.

[Note to other readers: The above suggestion is just for Cormie.]

peasant

cormie wrote: »

Think that was the reason I was given aswell. Something about it being good for the black smoke that comes out when the revs go up..

Make sure your injection pump and timing is properly adjusted and that should put an end to the (excessive) black smoke as well.

peasant

However ...if you add two-stroke ouil to your tank (at a ratio of 1:200), that WILL do your engine good. As the oil will luibricate your injectors just that bit better than the new, clean, sulphur free diesel can, it will prolong engine life and save just enough fuel to justify buying the oil in the first place.

cormie

I don't have black smoke luckily Was just something someone told me some time ago so thought I'd ask.

Esel, it WOULD save me money since the 3/5 litres of petrol would be cheaper than 3/5 litres of Diesel

snowman707

a friend of mine recently filled his jeep with petrol by mistake & drove about 3 miles out the road before it started spluttering , we towed it home , drained the tank, changed the filter. put in a gallon or so of diesel to see would it start, started ok & then we filled the tank to dilute any traces of petrol left. driving away with no ill effects.

Run_to_da_hills

snowman707 wrote: »

a friend of mine recently filled his jeep with petrol by mistake & drove about 3 miles out the road before it started spluttering , we towed it home , drained the tank, changed the filter. put in a gallon or so of diesel to see would it start, started ok & then we filled the tank to dilute any traces of petrol left. driving away with no ill effects.

You are luck you caught it at 3 miles any further could have fu**ed up the fuel pump. Petrol cannot lubricate the cams or followers on the inside of the pump so they overheats with the friction and wear out the case hardening.

http://www.thedieseldoctor.net/Results-of-fuel-contamination-in-Diesel-systems