I just used this in my roommates 97 Grand Cherokee 4.0L . She bought it recently for 1k with alot of miles , anyways it has been leaving a nice stain on the driveway which was quicky diagnosed as a rear main seal. Not having the time to replace the rear main seal for her , I suggest to try this stuff . I was really skeptical it would work ,but too my surprise it has lost a drop of oil in a week. Thoughts on this? I suspect that when this is drained out that the seal swelling will stop.