Opinion : Using Diesel as an oil flush

[Grega]

Of late i've heard a few good and bad things about using diesel in your oil to act as a flushing agent to remove crud ect from years of (lack of oil changes), solidified oil, ect ect.

I've never done it personally, my mate whos a mechanic of 20 years swears dead against it.

Anyone have any personal experience with this? Is that all those engine flush (pre oil change additives) things really are?

Thoughts/comments appreciated.

[roadsailing]

i have heard of this as a "running rebuild" where you drop the poil, fill with diesel, run the engine for 5 minutes, run the engine for 5 minutes, drop the deisel then fill it up with oil then. the next step is always "sell the car" so it can;t be that good.

i talked to a guy at work who did this ages ago, the result was a f*cked engine. i dont think it could be all that good, maybeye use deisel oil as a less extreme course, it has detergent and gear in it, but i would imagin it is pretty thick.

[ace]

Can't use the oil flush products?

[river]

Hi,

It's often the build up of crud and deposits that stop the oil leaks. Once you clean it all out you may find the engine burns more oil and leaks.

Of course, if you're doing a full engine rebuild this isn't a problem, but it can be on an old engine that you aren't intending to rebuild.

seeyuzz
river

[bnicho]

Don't do it! I know someone who tried this on a Mini engine on the advice of a so-called mechanic. Oil pressure was 50psi at 3000rpm beforehand, 15psi at 3000 rpm afterwards.

Proper flushing oil is thicker than diesel.

[Billzilla]

Belt the car down the highway and get it nice & hot, then dump the oil.
Wait until there's one drop every minute or so, then start the engine for a couple of seconds at idle. Then change the oil filter (add some fresh oil to it before fitting if you can) then wait again for the drips to nearly stop and fill it with oil.
Disconnect the coil lead and crank the engine for a few seconds, then reconnect and start it normally to idle until the oil pressure comes back.

That's all you need to do.

[ra40celica]

Belt the car down the highway and get it nice & hot, then dump the oil.
Wait until there's one drop every minute or so, then start the engine for a couple of seconds at idle. Then change the oil filter (add some fresh oil to it before fitting if you can) then wait again for the drips to nearly stop and fill it with oil.
Disconnect the coil lead and crank the engine for a few seconds, then reconnect and start it normally to idle until the oil pressure comes back.

That's all you need to do.

yes lets all start our engines with no oil.

[thechuckster]

actually - when you drain the sump there is still oil in the filter, pump and most of the oil galleries. When you di the above trick you're merely pushing all that remaining oil out of the system.

personally, i'd do it with no spark and the plugs removed but unlike Bill, i don't have long history in motorsport engineering.


edit: the trick offlushing with diesel is very handy for an old engine that's been sitting for a long period of time. The light oil will remove the caked and dried crud from the interior of the enigne.

[minorobsession]

Not sure why everyone gets so hung up about whats on the inside of there engine! If it got crap stuck to it the engine is either old or has not had regular oil changes so not worth worrying about.

Diesel or anything like it has little or no lubrication value so you will cause metal to metal contact.

If it is stuck to the inside of the engine leave it there! puting anything in the oil system to wash it into the oil system means that it is going to pass throught you bearings like a liquid abrasive!!!!!!!!!!!!!!!

If you are worried about the little bit of black oil left in the system when you drain the oil CHANGE YOUR OIL AND FILTER MORE OFTEN this will also tend to clean the inside of the engine if you can not bear the idea of it being dirty. Remember if your filter is blocked it will by passed unfiltered oil.

[myne]

Done it. Only for short periods.

Though I know a mechanic that helped out a friend of his...
Laser KA.
Never had an oil change in 10+ years. Only top ups.
Siezed the cam.
Inside the head the oil had CRYSTALISED. I chipped a bit off, dropped it on the ground and it went "chink!"
So, he tapped the cam loose, sanded the bearing surfaces, chiseled as much crap as possible out, refitted it, new belt etc, filled the engine to the top with diesel to soak overnight, it leaked out obviously but it did its job, ran it for a while on diesel, drained, ran again on diesel, drained, drove it for a week on diesel, then flushed and added oil.

I think he may have added 2 stroke oil to the fuel aswell.

But that engine surprisingly ran fine once that was all done. The oil pressure was pretty decent and it, as far as I know ran for ages. Hell, it might still be running.
I think the real key was that it was treated REALLY gently during the cleaning process.

[Billzilla]

yes lets all start our engines with no oil.

I'm only talking a couple of seconds, and with the throttle closed there's a goodly vacuum in the engine so very little load on the bearings. They'll still have more than enough oil on them so nothing gets damaged.

It's amazing how much abuse an engine can take before it goes bang anyway - Last year at the PF party we rigged up an old Subaru N/A engine with full throttle and no water. Managed to get it started, then after about 13 minutes of screaming it's tits off at full thottle with no load .... the little fuel tank we had it sucking from ran out!
So we filled it up again, dropped the oil, and after a bit of mucking around got it running again. After another few minutes it started to slow down, and finally slowed enough to stop. It was so hot the metal all through it was literally crackling .... we were worried it'd set the grass on fire.
Now I'm not suggesting running and engine without oil is a good thing, but for a couple of seconds it's really not going to hurt anything.
Though as mentioned above, if you want to remove the plugs and wind it over on the starter that's certainly a good idea.

[ViPeR_NiPPleX]

wow, this is nuts, i was told yesterday about using diesel to free up seized hydraulic lifters in a motor from a mechanic.... i think i'll just pull em out and clean em.

[bimmerskickass2]

only problem with winding it over with the starter is the chance of burning out the starter, usually we drop about 1.5 litres of oil, put some diesel in and run it at idle fot 10mins or so, drop the oil, fill up with new oil, once had a car with a couple of sticky lifters so instead of using diesel, kero was used however i still swear against it as kero is a cutting/abrasive liquid, a bit too abrasive.

[slide86]

i ran a frontera engine for an hour on 4 litres of diesel and 1 litre of oil. there were no bad side effects and it cleaned the engine out really well.

the car had not been serviced for 60000km and the engine ran out of oil. customer then drove it 800m with oil light on. i flushed the engine and did a service and now its running sweet as again.

a mate ran his rb26dett in r32 gtr on diesel for 5 minutes to clean it out. nothing bad happened there either.

[nihilism]

the car had not been serviced for 60000km and the engine ran out of oil. customer then drove it 800m with oil light on. i flushed the engine and did a service and now its running sweet as again.
.

Are people really that stupid?

Some people don't deserve cars.