I have a 1992 Buick Roadmaster with the 5.7L V8 and the car has 180,000 miles on it currently. I have been putting in Pennsoils 10W-30 normal motor oil and I would like to know if this is ok to be doing. I have been doing this for a few years and just want to make sure that the car is ok for this weight of oil and if it should have a thicker oil or thinner oil and what that oil would be?