[geeteeohguy]

Originally Posted by b-man

Probably the worst thing you can do is use some chemicals in your crankcase to break free a bunch of crud all at once that was fine if left where it was deposited. Clogging up your oil pickup screen and damaging an otherwise okay engine is your reward.

There are products which are formulated to slowly clean up deposits and unstick lifters and such but backyard use whatever comes to mind or happen to have on hand methods are questionable at best.

In the 1980's the outfit I worked for started pushing an 'engine oil flush' upsell on the regular oil and filter change. I wouldn't recommend them and got some heat. We bought a few engines, mostly for the older customers who lived in a nearby retirement community and who drove pristine, low mileage '60's and '70's cars that were full of sludge and carbon from all the one mile trips they made to the store or to church. The solvent we used would break up sludge and coke and it would enter the oiling system and clog things up and a bearing would go south. Just like a blood clot. BAD idea. The best way for a clean engine is to maintain it in the first place.