GMC Sierra 2008 Used Automatic Gasoline mileage: 300 KM or more Engine 6 liter installed and 6-speed transmission installed. The transmission needs a gear module. It has headers, Y-pipe, and K&N intake. It comes with a new BTM kit that I haven't installed. It has a custom tune for throttle response and torque. Color changed to black. Mileage is 265 on the original odometer. I changed the odometer because the airbag light is on. No 4WD.