LordWayback
Full Access Member
- Joined
- Jun 23, 2022
- Posts
- 556
- Reaction score
- 436
4lslippy bad plugs low miles, factory gears with tons of junk 13.5 it’s insaneA GMT800 isn't gonna get 18mpg, no way, no how.
A 900 might have a shot with newer engine cals, AFM, the 3.08 rear and the six speed.
Tires make a huge difference. You want a rock-hard compound in a highway tire. I know my Goodyear Duratracs might be costing me as much as 2 MPG.