Diesel fuel or kerosene also makes a pretty good running cleaner, as long as there's no load placed on the engine while it's in there. Dump in about a quart right before an oil change, and run it at fast idle, no load for about 15 minutes. If you've got a canister-type oil filter, remove the filter element first, no sense cleaning the filter and dumping the dirt back into the engine.
Gulf Oil Co. used to sell an engine cleaner that would actually take carbon deposits out from under piston rings, but it was a "professional-only" product that they only sold to certain shops. No over-the-counter sales of that product at all! The family shop used it back in the 1950's before doing an engine overhaul. It cut down on cleanup after disassembly by at least 50%.
Jerry
