I'm keeping this simple and letting the pics do the talking for me. 2020 Silverado Trail Boss LT with 6.2. At about 97,500 miles on the odometer the serpentine belt was squeaking. Other than at initial purchase, the belt was been quiet. At purchase I had a "warranty repair" done where the dealer applied some belt dressing to quiet it down. At this point, even though the owner's manual says to place the serpentine belt at 150,000, I decided i was going to do it at 100,000. When I replaced my spark plugs and wires at 97,500 I also sprayed at stop squeal on the belt. It worked. At that time I noticed fraying on the belt edges. Yesterday I crossed 100,000 miles on the truck, so today I decided to replace both belts. The ac belt was flawless and didn't need replacing, but I figured I'd do both at the same time. In the first picture you'll see the old belt on the left and the new belt on the right. Both are OEM, so this is an apples too apples comparison. I did find fibers from the serpentine belt inside the alternator vent holes at the top. I also replaced the idler pulley. There was a mess of fibers twisted around the bolt on the backside of the pulley.