Outer Limits 4x4 Board

A mechanic recommended I put a litre or so of petrol in with my full tank of diesel to give it a bit more go and get better economy.

Too scared to do so but what are the thoughts out there? Is it a common thing that people do?

DONT DO IT

wouldnt put any more than a teaspoon

wouldnt even do that

There was a big thread on here a while ago about doing it, some say it's all right and some said not to.

I have done it i went 10% petrol in my 1HZ, it made a fair differance, i don't do it all the time but every so often i'll give it a drink .

I was told that it can damage you're pump if i did it to often, from my brother in law(diesal mech), but so far no damage yet .

tna racing wrote:DONT DO IT

wouldnt put any more than a teaspoon

wouldnt even do that

Why's that?

joel HJ60 wrote:

tna racing wrote:DONT DO IT

wouldnt put any more than a teaspoon

wouldnt even do that

Why's that?

seen a deisel go bang from this

not worth the strain

tna racing wrote:

joel HJ60 wrote:

tna racing wrote:DONT DO IT

wouldnt put any more than a teaspoon

wouldnt even do that

Why's that?

seen a deisel go bang from this

not worth the strain

Go bang how?

injector pump let go after 100kms

of putting petty in tank

So the engine didn't die, the pump let go. I'm curious to know how petrol would do this?

well no fuel in a motor isnt really good.

i have been told it is due to the octane levels in fuel, any one wanna shed some light?

A mate said its actually in the Nissan Patrol owners handbook, said something about adding a certian amount is ok in cooler conditions or something like that ??

Well to start with diesel is an oil, so it lubricates. Petrol is not. It also burns at a different temprature.

Zeyphly wrote:Well to start with diesel is an oil, so it lubricates. Petrol is not. It also burns at a different temprature.

I knew this much. So the petrol is causing the pump to die due to no lube?

joel HJ60 wrote:

Zeyphly wrote:Well to start with diesel is an oil, so it lubricates. Petrol is not. It also burns at a different temprature.

I knew this much. So the petrol is causing the pump to die due to no lube?

could of been

been told by the australian tech rep for lamborgini tractors that the go in turbo diesels paricularly is to use a small amout (a litre or two) of kero in a full tank. Apparently petrol runs too hot and causes preignition in diesels which is hard to pick in a normally rattley engine its supposed to be worse in turbos as they need the higher octane.
kero supposedly does a good job of removing carbon and tarnish buildups and runs only a little hotter.
lamborgini recommend it every 3rd to 5 th tank also good to stop iceing of fuel

Ive been useing it in my canter truck for two years no dramas
hope this helps
cheers andrew

joel HJ60 wrote:

Zeyphly wrote:Well to start with diesel is an oil, so it lubricates. Petrol is not. It also burns at a different temprature.

I knew this much. So the petrol is causing the pump to die due to no lube?

That would most likely be the reason.

And as far as Nissan handbook recommending it in cold conditions, might have something to do with helping the diesel remain more fluid in really cold temps.

I did it a couple of times in my Rocky. Didn't notice that great of a difference so I didn't bother to continue. Didn't hurt the engine or pump. I put 5L of petty in with 40L of diesel.

also petrol engines have a comp ratio of about 9-1 to say 13-1 where as a diesel is about minimum 18-1 so imagine how bad it would ping if you put alot in.

tna racing wrote:DONT DO IT

wouldnt put any more than a teaspoon

wouldnt even do that

I've posted this before.
... after a ~36hr shift, I put in bout 1/4-1/2 a tank of ULP in GQ..

Nearly asleep on my feet, I couldnt understand why it was so cheap, until I looked at the pump and realised it was the ULP Price up there.

Some prick had swapped all the fillers up at the servo and in my dozey state I didnt realise.

Tried talking to Apu in the shop to get something to drain it into that was a waste of time, so all I could do was fill up rest with Diesel, and drove home at bout 40-60kph, no load on it.. most is flat road home..

I drove from FTG and Springvale road Shell there to Langy down Monash. No ill affects at all.

Drained it out next morning, and drove the few mtrs to the servo.. New Fuel filter, prime and done...

Car is still going strong 100k klms or more later, well apart from the gearbox in it.

I wouldnt do it deliberately, but its not the end of the earth, but then, I could have just been lucky as hell.

Detonation is the first problem, then having components that have a clearance of 2 microns being lubricated by a dry fuel.

Do it at your own risk. If it was meant to be it would be in the fuel now.





Andy

I'm not a diesel expert, I don't even own a diesel powered engine. But my basic knowledge of them is that the air is compressed and then the diesel is injected and it burns as it comes into contact with the hot air. As opposed to petrol engines, the petrol mixes with the air as it enters the cylinder, then the mixture is compressed and ignited.
So, if the diesel is burning up as it is injected into the cylinder, how can you get detonation or pinging?

On a slightly related subject, a mate of mine has a diesel gemini and it wouldn't start because some "smart" cookie decided to wire the glow plugs up to an in-cabin pushbutton without using a relay, nor appropriate sized button/wires. It ended up melting the contacts on the button which left the glow plugs on and burnt them all out. The guy from RACQ managed to get the engine started by pouring some petrol on a rag and holding it in the airbox so the engine was breathing the petrol vapours (and presumably it ping/detonated a few times) but it was enough to get it started.

oldest trick in the book to clean injectors etc.1-2 litres petrol to tank of deisel.In a petrol motor put 1-2 litres of deisel.Have a look at the commercial injector cleaners for deisel it tells you it's 90% petrol and for petrol it tells you it is 90% distillate,just read the cans.
You only need to do it every 3 months or so(depending on milage).

ajsr wrote:been told by the australian tech rep for lamborgini tractors that the go in turbo diesels paricularly is to use a small amout (a litre or two) of kero in a full tank. Apparently petrol runs too hot and causes preignition in diesels which is hard to pick in a normally rattley engine its supposed to be worse in turbos as they need the higher octane.
kero supposedly does a good job of removing carbon and tarnish buildups and runs only a little hotter.
lamborgini recommend it every 3rd to 5 th tank also good to stop iceing of fuel

Ive been useing it in my canter truck for two years no dramas
hope this helps
cheers andrew

I've heard of this before, the kero also absorbs any water in the tank and allows it to gt burnt in the combustion process

So far alot have truths have been told. But there is no true or false answer.
As for the petrol cleaning diesel injectors, it is a very good injector cleaner. At a ratio 1:100 it will clean your diesel injectors.
It is a dry fuel and it will dry out seals in your injector pump and as andy mentioned there as some very tight tolerances in an injector pump that are only lubricated by the fuel.
Petrol will ignite earlier than diesel in the combustion process and hence it will cause detonation. Once the fuel ignites it ignites the diesel earlier than it may have with out the petrol in it.
I havew a supercharged 2H in a 60 series. I put a couple of litres into a 170l tank every now and then. I've been doing it for about 150,000km and the engine now has around 360,000km on the clock with no ill effects that i'm aware of.
If i had a late mode common rail diesel, a nissan ZD30 engine or similar, i wouldn't do it! But on an old clunker where tolerances aren't as tight and the engines are a little more forgiving i'd be happy to do it.

Using small amounts of acetone in your fuel will also help clean, and atomise the fuel.
Very small amounts required, ie under 1%.
Google it or search my posts on this before.

no affects on fuel/ hoses/ lubricity at that level, but it acts as a wetting agent, and helps the fuel to atomise better, plus it cleans up the fuel system.

Used it with great success in both petty, and diesel.

Trains

ajsr wrote:been told by the australian tech rep for lamborgini tractors that the go in turbo diesels paricularly is to use a small amout (a litre or two) of kero in a full tank. Apparently petrol runs too hot and causes preignition in diesels which is hard to pick in a normally rattley engine its supposed to be worse in turbos as they need the higher octane.
kero supposedly does a good job of removing carbon and tarnish buildups and runs only a little hotter.
lamborgini recommend it every 3rd to 5 th tank also good to stop iceing of fuel

Ive been useing it in my canter truck for two years no dramas
hope this helps
cheers andrew

How can petrol cause preignition in a diesel ? Given the fact that injection is timed, how can what hasn't been injected pre ignite ?

Also diesel systems use cetane rating not octane - the things are supposed to detonate - it their operating principle

I'm not going pro or con, but some of the info seems wrong.

from wat they taught me at tafe, when you start injecting fuel in to a diesel engine there is a delay between when injection starts and when the fuel starts to burn, they said if you mix petrol in that this delay doesnt occur and that the fuel burns straight away which can cause damage to the tip of the injectors, also as it starts burning straight away the piston is in the wrong postion when the power stroke starts.
thats just wat i was taught at tafe

mundy

Yes - ignition delay is a factor with diesel engines, severely limiting theoretical maximum RPM. Petrol addition significantly reduces this delay and so can raise the obtainable upper RPM of a diesel engine. This of course assumes the engine is mechanically capable of higher RPM and many aren't.

However the overall situation is far more complex, combustion rates, thermal loads and cylinder pressures change significantly - things that could easily lead to engine damage.

The difference in lubrication for injection components is a also a factor to consider. Differences in normal diesel concern the manufacturers let alone "home brew" fuels.

I'd be very cautious with a road application - especially if reliability was a priority.

MightyMouse wrote:How can petrol cause preignition in a diesel ? Given the fact that injection is timed, how can what hasn't been injected pre ignite ?

I think you just answered this question....

Here....

MightyMouse wrote:Yes - ignition delay is a factor with diesel engines, severely limiting theoretical maximum RPM. Petrol addition significantly reduces this delay and so can raise the obtainable upper RPM of a diesel engine

If the petrol reduces the delay then the fuel is burning before it should!!

when you run wvo you can run a mix ox straight wvo and ulp.
all good.

ALSO,

i am pretty sure some manufacturers reccomend adding small amounts of petrol to diesel in cold climates.

Jes

Parrafin and Olefin content is most important in diesel, as this governs cetane rating (note that CETANE rating is important, not octane rating).

Most diesel injector cleaners are just naptha - which is a fraction in between petrol and diesel (but you only put a few hundred ml in a tank).

In VERY cold climates, many manufacturers say it is OK to mix up to 50% petrol with diesel in WINTER, to prevent waxing and reduce viscosity. HOWEVER - we are talking -30 or lower here, and at those temps, cold starts kill engines rapidly. Engines seem to have a much shorter lifespan in northern europe.

Diesel engines can still preignite. Diesel burns slower than petrol, so the petrol makes the flame front move faster. All diesels I know of inject the fuel before TDC, and the injection timing is set up for the engine, based on SAE(XX) standard diesel fuel.

I definitely wouldn't add petrol in summer.

MightyMouse wrote:

ajsr wrote:been told by the australian tech rep for lamborgini tractors that the go in turbo diesels paricularly is to use a small amout (a litre or two) of kero in a full tank. Apparently petrol runs too hot and causes preignition in diesels which is hard to pick in a normally rattley engine its supposed to be worse in turbos as they need the higher octane.
kero supposedly does a good job of removing carbon and tarnish buildups and runs only a little hotter.
lamborgini recommend it every 3rd to 5 th tank also good to stop iceing of fuel

Ive been useing it in my canter truck for two years no dramas
hope this helps
cheers andrew

How can petrol cause preignition in a diesel ? Given the fact that injection is timed, how can what hasn't been injected pre ignite ?

Also diesel systems use cetane rating not octane - the things are supposed to detonate - it their operating principle

I'm not going pro or con, but some of the info seems wrong.

Don't know dude as I said at the top I was told by a Lamorgini tractor head tech rep for all australia.the bloke is married to good mates sister
its all second hand info im afraid.Im just a dumb panel beater by trade and now in construction.on new direct inject diesels isnt the fuel injected staight to to cylinder or intake port??
maybe he said cetane or maybe he said octane so a dick like me followed??? All i know is that he said kero was a far better option than petrol
cheers andrew