...That I can't answer off the top of my head... A friend & I were driving along, when we spotted 3 deisels running along at about 50 MPH. He asked "Hey, only the front engine has its lights on. Does that mean that is the only powered unit???" ----- "Oh I guess having only One unit powered out of 3 uses less fuel..." I said " I have no bloody idea" Well how about it?? Anyone know if you use more fuel "Towing with One unit" than if all 3 were powered???? I would figure on "3 powered" uses more fuel than "One towing 2"