What's the 2003 Chevy silverado 4.8 Oil type?

The 2003 Chevrolet Silverado expects a SAE synthetic 5W-30 oil for its engine; You should use this for all temperatures in Your truck, according to GM, for the 5.3L 8 cylinder engines. It'll take 6 quarts of it when You've installed a new empty filter, and You shouldn't go over 18 pound feet of torque on the oil pan's drain plug. Filter wise, You can use any standard canister style off-the-shelf one, but the WIX57060-EA has a good reputation for compatibility and performance on this vehicle, and runs about $10 at Your local brick and mortar car parts store.