I've read many many posts and seem comfortable with what I am doing with my truck now but I'd like to get some opinions from everyone. Price is beginning to be a concern lately so keep that in mind. I've never done a UOA and I probalby will not have the funds to do one in the near future hence the price beginning to be a concern. Vehicle 03 Silverado 5.3 liter. 38,000 miles. Used dealer oil for first two changes at 1600 miles, and 5000 miles. Since then I have used Mobile 1 5w-30 at intervals coresponding closely to my GM oil life meter. I tend to change around 20% of oil life remaing which seems to vary between 5000 and 7000 miles. The 7000 mile interval included a 3500 mile road trip. While I feel comfortable doing this I have been toying with the Idea of going back to Dino oil for cost reasons. I plan to keep this truck as long as it is economically viable which I hope is near 200k. What kind of oil would you use and why? I'm thinking of switching to Penzoil for the summer and maybe going back to M1 in the winter. The truck is driven a mix of conditions. I pull trailers on some weekend trips usually 500 miles or more. Max trailer weight being around 3000lb. During the week my wife drives the truck to work which is 22 one way miles of varying hiway stop and go. Should I bite the bullet and stick with Synthetic or should I be ok going back and forth with dino syn? I'll save the info on my other car for another post someday. Thanks for all opinions!