After reading of how good the stuff cleans out an engine and seals i figured id try it b/c i have a very slight rear main seal leak. Well i ran it for 512 miles and just changed my filter and oil and i can say that i can tell no difference whatsoever. The oil still looked clean and the slight leak is still there. I followed the directions and even used delvac to top off the oil when i had to swap filters (took a lil over 1 quart). i feel its snake oil. Just thought id share what i noticed.