I almost never drive on the highway, just in town, so my speeds never really exceed 55mph. I still have the stock 3.92's with 35' tires and I can really tell that it takes more to move and for that matter stop my truck. and the load on the engine has a greater effect on fuel economey than RPM's alone. sure the RPMs went up but the load on the engine went down. 'THREE HUNDRED RPM's' BUT better, I gaind 'mechanical advantage' which helps move the truck from a dead stop with less effort (less fuel) and it in a higher power band at 60MPH which gives it better fuel economey. At 60MPH, I only gained 300 RPM's from the 3.55 to the 4.56's.
