I have been so surprised to see all of the questions asking about fuel economy, tank size and spare fuel, so I am happy to finally answer some of these questions. A lot of folks don't realize the potential of a 12v cummins, but they are a remarkably efficient engine, sometimes reaching up to 30 mpg. With this rig, having 4.10 gears and the equipment, I am getting about 20 22 mpg, and I am very satisfied with that. I think once I go up a tire size it will improve even further. I do not currently pack any spare diesel, but we will see what adventures come along in the future.