The factor determining fuel use is how many times a piston goes up and down in one mile. Every other time it takes in a mixture of one part fuel to fifteen parts air so the more times it goes up and down the more fuel it will use. The ONLY way to slow the piston cycles down is through gearing. That's the physics, but in the real world gearing can be too shallow which leads to an open throttle/low manifold vacuum condition that uses fuel, tire type and inflation, wheel alignment(front and rear), increased friction like brakes dragging and dry or tight/loose bearings, engine temp too low, carb not adjusted correctly, state of tune, free flowing exhaust but NOT large diameter pipes, and the most important factor IS THE DRIVER. Our shop truck goes through a tank every two days with one driver and every three days with the other.
