How to get rid of oil "varnish"?

[byron]

What's a good way to get rid of oil "varnish" build-up on an old but still very good 3.5 in a RR Classic1989.....

I've heard of doing an oil change and running it with Diesel Oil for a couple of thousand Klms, Diesel Oil is high detergent and "scrubs" the deposits off.......

or, running it with 2 litres of ATF in the sump after draining/getting out same quantity of old oil......for a couple of hours.......doing an oil+filter change

or, putting 2 litres of Dieseline into sump same as with the ATF......

or, running it for 15-20 mins topped up, overfull with 2 litres of kerosene and then changing oil and filter.

Which of the above should be most effective AND SAFEST?

[harry]

err, byron, why do you want to do this,?
the old days of having to 'decoke' an engine are gone, modern oils solved that years ago.
we use high detergent oil in aircraft all the time, thats ok for them, sticking atf in seems to me to be a good reason to replace bearings, so if you want to do that, save the price of the oil and just strip the engine now.
if the engine runs ok then just leave it alone and don't mess around with silly ideas.
if it isn't dropping a lot of oil now then if you do any of your suggestions it will clean the existing seal areas and commence leaking heaps.
if you just want to see clean oul then change it lots.
putting in a flushing oil or other will clean it up, but the existing coatings on the seals, cylinder walls, etc will be deteriorated and the engine will pump oil and leak oil.
back to 'why do you want to do this?'

[gruntfuttock]

I'm with Harry on this one.
If it aint broke don't fix it

[byron]

err, byron, why do you want to do this,?
the old days of having to 'decoke' an engine are gone, modern oils solved that years ago.
we use high detergent oil in aircraft all the time, thats ok for them, sticking atf in seems to me to be a good reason to replace bearings, so if you want to do that, save the price of the oil and just strip the engine now.
if the engine runs ok then just leave it alone and don't mess around with silly ideas.
if it isn't dropping a lot of oil now then if you do any of your suggestions it will clean the existing seal areas and commence leaking heaps.
if you just want to see clean oul then change it lots.
putting in a flushing oil or other will clean it up, but the existing coatings on the seals, cylinder walls, etc will be deteriorated and the engine will pump oil and leak oil.
back to 'why do you want to do this?'

My mate wants to get rid of these deposits coz they wouldn't be there if the truck he bought recently had been run on synthetic oils from new......my P38a has been on Mobil 1 since it's after original run-in oil and looks like new!......no visible deposits so I would suppose it has clear oil galleries, clean, unvarnished bearings,etc all other parts in contact with oil so that it gets correct amount and pressure of oil, is able to shed heat etc ALL the other purposes that oil is used for without the minuses of dirt and oil waste by-products baked on to engine and its parts not serving any useful purpose and causing both potential and possible minor detremental problems already........is that a good enough reason to want a clean engine internally? ...........

OR do you think the varnish, old baked on oil, grime, dirt and various accretions of microscopic rubbish may have worthwhile benefits that I may have overlooked???????

[gruntfuttock]

The fact is that if you take out all the "Varnish" that is in there you will have trouble with the motor. The motor has got used to running like this. Yours had a different oil from new, you cannot compare the two. Trust me. Been there, done that, and had the bills to prove it. But if you want to go ahead and do it, by all means, get rid of all that "Varnish". But just don't whinge when things start to wear and leak.

[JohnE]

Not wishing to sound stupid but how did your mate find the glaze in the cylinders. By pulling it apart I suspect,if its apart, put in new bits and he won't have to worry.
An old bushie told his method of getting rid of glazing on tractor pots, work them hard, his method involved low speed ploughing.
I guess if we all worried about the innards of our engines to that degree, they would be apart every weekend for a flush and clean.


john

[MacMan]

I agree. Your mate can spend money on rebuilding one of two ways. 1) When he needs to after things start failing sometime yet to be determined. 2) When he needs to after he encourages failures by flushing it.

Your concerns about "blocked oil galleries" are only worthy if things are failing. I know of one bloke who decided his new Suzuki trailbike needed the old oil-out-and-kero-in-the-sump flush for the health of the engine. He had a total engine failure in no time flat.

If it runs smooth and quiet, has good compression, a happy cooling system and produces power just service it normally and drive it normally.