Personally I use Valvoline full synthetic motor oil in my 1998 K-1500 and my 2015 Chevy Malibu. But there are people who swear by oils lke Amsoil. The Dexos rating and viscocity are the most importatnt things,besides changing the oil and oil filter on time. If you go through lots of dust, water crossings or do mostly city driving or pull a trailer, its best to change it eaelier.and always use the proper viscosity called for with the right Dexos rating. The oil filter is very important too, and I prefer Purolator, or ACDelco brand oil filters.Dont forget the air cleaner if you are off-road,alot in dusty conidtions... .