My truck had Pennzoil 10W30 ran in it with whatever filters the PO's mechanic used, and had the oil changed every 3K; I kept up the Pennzoil, but swapped to AC Delco filters.
I eventually switched to Amsoil 10W30 and WIX/NAPA filters in my truck, and I can say right away going from the standard to the synthetic has made a lot more of a difference than I though it would.
Replacements parts I try to buy the top of the line stuff. NAPA parts seem to be better quality than the other parts stores, it's hard to swing AC Delco sometimes because none of the parts stores carry anything in store, it's all special order.