Pilots and aviation mechanics (A&P) use it frequently for it's ability to dislodge glaze from cylinders and heads. Remember aircraft are air cooled and meticulously maintained (should be at least).
The stuff is basically a lot of mineral oil and some mineral spirits with a little bit of benzene solvents to cut oil that becomes plasticized from high heat (think outside cast iron skille)t.
Anyplace you see that crusty black stuff or amber colored buildup n parts when disassembling an engine will be cleaner if you use this stuff in oil and fuel. Using it one needs to stay up on oil change intervals and filter changes. If used on old engines checking the oil pickup screen is a good idea. I recall seeing "experienced" engines that died of oil starvation after the stuff was used and the pickup was plugged solid. Regardless wearing surfaces generally stay clean (cam lobes and lifters, cyl walls, bearings) and the area around ring lands do stay clean.
If using synthetic the best I method I recall was to put it in about 1,000 mi before a filter change, repeat every change.

My gut feeling is the benzene solvents really do the work and the mineral oil and spirits thin and mix with the oil to get the solvents into the lube circuits and carry the crud away to the oil filter.
Which reminds me use high quality filters so as to trap the crud.