I have only ever used techron in any vehicle I have ever owned. As far as I am concerned, it is the only off the shelf brand that works.
Things to look for include
the 35R wave plate issue where a plate inside the transmission fractures due to improper heat treatment at the factory. You will see shift flares with your RPM go up the vehicle shifts late. May also lose reverse. This a full transmission rebuild or reman replacement. If you're lucky, it has already happened to the previous owner. If not it's a time bomb of sorts. All 6T70 transmissions throughout the GM line suffered this issue in 2008. I should say we're prone to this issues starting in 2008.
Brakes dragging
The small rubber brake lines that connect from the steel brake lines to the calipers degrade over time. They pass fluid properly to the calipers to close the pads on the disc, but they collapse internally, keeping the brake fluid from flowing back towards the master cylinder and leaving the brakes partially clamped to the rotors. Others have claimed that adjustment of the power booster for the brakes can also correct this. I don't know if it's true
I owned one of these vehicles until I got into a 5 mile an hour fender bender where I tapped car, accordioned my hood, and that was that. I experienced the wave plate failure but not the brake issue
