actually with all the work you would need to do to make that work it really would probably get worse gas mileage due to weigh tof vehicle. put a vacuum gauge on it and use that as a guide , keepp it in econoomy range

At present time I am only getting 14.1 miles to the gallon, my wife bought it from a dealership, could it need a complete tune up. We went 500 miles on almost two tanks of gas, what could the problem's be. Very little city, expressway miles. had cruise on through mountains, but took overdrive off, so it wouldn't kick on and off going 68-72 miles per hour.
Can you give me a ball park figure how much it would cost.

trucks traditionally don't get as good of mileage as cars do. I't because they waeigh more and have different gear ratios. if you drive on eway you shold have overdirve on. About the only ting you can do is drive in overdrive on eway or actually whenever you are above 50 mph. replace filters like air and fuel onc year, and keepin good tune. you could try a tune up but don't expect much if anything. It's a truck and they aremade to haul loads, not like a car that isn't made to do thatespecially if you are going from something like a Honda Civic to a truck.