The oil cooler fittings (shown) and lines usually leak on high-mileage trucks, so we replaced them. We ordered these from a GM dealer. The fittings PN 15529401, hose PN 12472279, and PN 12472280. Next, we installed the fittings by applying sealer to threads, hand starting them, and tightening them to 18 lb-ft. Clips were installed by pushing them into fittings with one motion.