The other thing to consider, besides fuel costs, is engine life and the quality of life while in the truck.
We're used to our daily drivers having OD, which means we're used to lower engine RPM. You'd be surprised how much difference 20-percent more rpm makes while trying to carry on a conversation.
It's also hard on the engine. Why zing it down the highway at 3,000rpm, when different rear gears and an overdrive can put it at 1,700rpm?
-Brad
