4-1/2 months ago one of the teenagers from around my shop came in with a neglected 1988 oldsmobile cutlass 2.8 with 188,xxx miles on it that he just got from a friend because it leaked oil everywhere. We were busy and i told him to bring it back after the new year and i will help him, we changed the oil and we put in Pennzoil high mileage 5w30 and a new pcv valve he had to add a quart about every two weeks but then after a while he used less and less oil and the leak really slowed down he put about 2900 miles on it since then and the leak is almost stopped except from the oil sender which we replaced today. You can still see oil but it is not leaking nearly as bad as it was. Pennzoil high mileage worked really well on all the seals. I always used PHM and knew it would slow the leak but it is almost stopped and that even suprised me. This kid checks his oil almost every day.lol... It worked pretty quick in my opinion.