Take the tramp off, remove everything off the mast with the exception of the diamond wires and you reduce the windage a good amount.
Keep your vehicle in tip top shape, ie good pressure in the tires, clean air intake filter, change the oil every 3K miles and keep your cooling system in check as well. Everynow and then clean the fuel system and all of a sudden your MPG will go up.

Try it, it works wonders.