Is that one of those hitches that mount to the bottom of the bumper?

 

if there are maint issues like stated previously, your mpg will inherently be low. like mine has a decent exhaust leak thats hurting my mpg now. but doing a good tune up will make a huge difference. after my tune up i went from 8 to 12 mpg's. i started using my cruise control more which will help too. plugs, wires, cap and rotor, coil. seafoam the **** out of it lol which there is currently a good thread up on it now. do a good oil change will full synthetic oil and a decent filter. make sure your tires have good pressure in them. and the easiest way to improve your mpg's is to keep your foot off the gas. lol