MM49,
Do you have any idea what "up to" means for can be getting 17.9 MPG? Let me help you. Going downhill at 45 mph with a 30 mph tailwind with less than 1/8 tank or fuel and the only thing in the stripped down base single cab work truck is a 120 lb driver who never touches the go pedal or turns on the A/C and has all windows closed!
Now you know!
How that relates to a "tow vehicle" even Einstein would have reaal problems figuring it out because one of his famous quotes is: "Imagination is more important than knowledge"!