I had a 2004 Silverado ext cab with 5.3. Bought it new and it was totaled in a head on in 2011 with 151k on it. It ran and looked like new. Every 60k I did the tranny fluid exchange at my dealership. Replaced it with a loaded 2006 Siverado ext cab LT w/ 40k. Followed same maintenance schedule with it. Sold it this past Oct with 149k on it and it ran perfectly. I also used Mobil 1 in both trucks and changed when oil life indicated. Both trucks never used any oil or had any transmission issues. I bought a 2017 GMC Sierra Denali w/50k on it and will continue with same plan.