As you might expect, the smallest diesel engine on the lightest truck did well on the unloaded fuel-economy drive, while the newest, most powerful engines struggled.

The Dodge Ram is fairly legendary on its own, but the 1997 iteration, with a selection of massive, powerful engines, is particularly well-regarded.

2008 Dodge Ram 2500 Cummins Four-Digit Fuel Mapping - Diesel Tech A quest for 1,000 hp from a 6.7L Cummins ...

We spent time driving a Ram 2500 4x4 with single rear wheels, a 3500 4x4 with the 6.7-liter Cummins, and the Ram Power Wagon, the off-road-going heavy duty.