We made the switch from gas to Diesel in the mid 60's. 2 to 3 mpg for gas was quite common. And that was going loaded one way and empty the other way. I experienced even less than 2 loaded both ways or fighting a strong side wind. A Cummins Diesel would do 3 1/2 to 4 under the same conditions. We cut the drag axle off one of the models similar to the white one in spanky's photos to use as a yard truck. I think it took a couple of gallons of gas to build up air pressure to move a trailer. We sold the thing for scrap iron. I wish I had kept it. It had a good 637 and 5 speed over.