I have an 08 Sierra with a 5.3L engine. Just turned 6k miles. I dumped the oil at 1k and used Castrol and now my oil life monitor is telling me its about time to change the oil. I usually do it when it says 10-20%. I am thinking of going to synthetic oil but want your opinions. I have a very short commute. About 8 miles. But I do drive the truck good distances on the weekend. Should i stick with the dino oil or go synthetic? Also in either case what are the best dino and synthetic oils out there. I usually always run Castrol gtx in my vehicles and synthetic Shell Rotella in my bikes. Is that ok to run in truck too?