I have been using Fram for oil filters and what ever is on special on oil and the recommended weight which is 5W30 for my jimmy every 3000 miles, and every second oil change i add a bottle of Marvel Mystery Oil to the engine oil about 500 miles before i change it to ensure i get all the sludge and carbon build out of the engine.
1999 GMC TRUCKS SIERRA 1500 PICKUP 5.3L 8-cyl Engine Code [T]
All TEMPS......5W-30 Engine, with filter..........5.7 liters, After refill check oil level.