I use the NAPA dinosaur oil and sometimes their high mileage oil in my 1995 GMC K1500 5.7 TBI (175,000 miles) unless i want to increase leakage and then I run the NAPA synthetic. I put some Castrol synthetic in this winter cuz i happened to see some at Costco for cheap and thought i would try it. It's probably good that I did because, in spite of the climate change warnings that they push real hard up here in Canada, it was -39F here this morning.