i personally use the gunk every so often to clean out the engine(every 30k or so) i never had any ill affects from it. but as you said some stays in. but you have to figure a 4.o holds 6 qts you drain a quart before you put the gunk in. so you still have 5 quarts to dilute it. then after draining and replacing the filter you fill it back up with 6 qts of oil so it dilutes more.

out of all the jeeps in this town the d**n gremlin had to invade mine

I've done so much,with so little for so long i can practicly do anything with nothing