Our trucks are about as aerodynamic as a brick... so you'll never get "great" miles per gallon. Like the other guys have said, if you're up on your maintenance (plugs, wires, fuel filter, tire inflation, gearing ratio, etc) then you'll get 12-14 city, and about 16-18 highway. That's what I get in my 5.4L 4x4. The engine goodies like the GOTTS mod and the K&N air filters, tonneau cover, will just help with slight power increases and possible throttle response. That's been my experience anyways. Good luck!