I had an 01 Yukon with the 5.3 that developed increasingly louder cold engine knocking noises until we traded at 215K. I tried multiple brands of 5W30, dino and synthetic, and even 10W30. Nothing made any difference in the noise that I could tell. We sent it to it's next owner running great once it had a half a mile to warm up using only about a quart of oil every 2500 miles.