talked to a guy today with a 95 s10 4.3 v6 with 468000 miles, original engine never touched, guy bought the truck brand new in 95.. just regular tune ups, and oil changes every 3000 miles, said he changed the transmission fluid and filter once a year. i asked him what kind of oil he used and he said castrol 20w50 year round, forgot to ask him what kind of filter he used tho.