NHTSA Complaint #11417411 — 2016 GMC SIERRA 1500

-Engine gas consumption state 21 MPG Highway, 17 MPG Combined and 15 MPG City. When I started using this vehicle during the first weeks and months the best MPG I could get at the highway is 18.5 MPG with top tier gas such Shell & Chevron during the first 2 years and now Costco brand. Every since I bought it, the gas MPG have gone down around 0.5 MPG. The vehicle feels that it has to use more gas in order to perform. -The motor oil pump at times moves down from the 40 mark to the 20 when idle at traffic light and when it starts moving, it temporarily moves to the 60 mark. -The transmission is an 8 speed automatic. It has issues shifting to first gear, second gear and times 3rd gear. When driving at slow speeds like in traffic jams, mall parking lots or when you slow down at the traffic light and then turns green and you start accelerating again it feels harsh on gearing down and up, like someone rear ended your vehicle. -This truck has the Active Fuel Management (AFM) and it turns on even slower speeds and you feel how the engine and transmission struggle to really gear up and down. Like it never gears and tries to accelerate at a higher gear. Like in manual transmissions when you accelerate on a higher gear than at correct own it takes forever to reach the needed speed. -Even if all 8 pistons are on it feels as if I am running on a smaller engine like a V6 or V4. -The driver car seat feels that move a little like an 1/8 of an inch. -It just feels that something is wrong with motor and transmission.