I've had good results in cleaning an engine with Rislone. I put in a quart of Rislone in place of a quart of oil at a change along with a new filter. Then I just drive for a few thousand miles and change the oil to synthetic. The Rislone isn't exactly a cleaner, it has detergents and surfactants to let the oil penetrate and clean. The cleaning action is slower and I don't believe there is as much danger of large chunks of crud getting dislodged. In any case I've used this stuff on lots of engines and almost always had compression increase and oil consumption decrease.