well i have used ATF to clean the internal of the engines for year, i run about 75% regular cheap oil and 25% ATF
i run the engine at idle for about 15 minutes and drain the engine and repeat. once i have run the ATF twice i refill with clean 100% oil.
ATF has detergent in it and will clean out the oil passages from gunk and junk, depending on how bad the old oil looks i put new oil filters on both times.
Its been used many times some people run 10% for the duration of there oil change to keep the engine clean.
im sure there are sticklers who will say this is all wrong and they would never do it but my family has been doing this for a long time and my grandfathers Nissan pickup ran for 687,000 and he ran the 10% every oil change.
If you dont feel comfortable with a lubrication fluid like ATF you could try a dry diesel kerosene engine cleaner that could burn out your seals.