I have a 1995 geo prism with 94000 miles that has had a steady diet of mobil 1 since new.I always changed the oil once a year.For the last two years the car has had the morng puff of smoke out of the tail pipe from the ever famous valve stem seals that go bad on these engines.Six months ago I changed to formula shell and the puff of smoke is gone.Last month I did another oil change with shell oil, and still no smoke.Is this shell a wonder oil?