The manufacturers use the EPA numbers which are measured indoors with no air drag, much less towing or hauling a load or even with all the seats with passengers. Ford is even worse as they use very tall gears to get an extra 1 MPG highway that no one will ever see in real use.
It takes a fixed amount of work to move a weigh across the pavement and even more to move it up a hill and this includes the weight of the truck which is going to be about 6,000 lbs. for a 1/2 ton and 8,000 lbs. for a 3/4 or 1 ton. That work requires burning fuel. There is no magic here and there is no free lunch unless you are a billionaire and making use of government subsidies.
