Living in the Colorado mountains we are always going up or down hill. The DD owners manual states that on a long pull to select a gear that will pull the hill and then set the cruise control for the speed that works. This will always peg the boost meter at 30. Have not had heating problems doing this. The cruise not only controls the speed but also the fuel. Think the DD brain is smarter than I am about how much fuel to put to the engine. Seems I read somewhere that this will produce more horsepower than manually fueling the engine.