Originally Posted by Goldengriff
With all the undercarriage protection on the trailhawk I'm surprised that extra weight dose not cause an mpg hit.
The extra weight would affect economy under acceleration (city) but not so much for highway. The skid plates, if they smooth out the undercarriage airflow, might actually help on the highway.
The additional 9 speed gearing in the city isn't much help other than to offer better acceleration. The acceleration of mass (work done) is the same moving the vehicle.
On the highway, the additional gearing allows lower rpm's and better economy without sacrificing acceleration in lower gears. With 9 speeds, there's an optimal gear for every speed to keep the engine at peak power for performance, or peak efficiency when cruising.
I'm impressed with Jeep's power train advancements!