Have a 1990 toy. celica gt with the org. rear main seal. Put 1 bottle in with a fresh oil change..The car does mainly short trips, and for first 2 weeks really no difference, but then after taking a few highway hour or so trips, it worked by the 3rd week...Rear main seal leak stopped and its been about 2 months now..So I think the key is highway speed trips to really get it to work and heat it up.....I've tried them all, and nothing worked or even came close to AT-205, some even made it worse....Will change the oil next week and use another bottle and see what happens...So far so good....