Change spark plugs, check spark plug wires, check distributor cap and rotor, change filter, change pcv valve, change your oil, change the filter oil, change the fuel filter, check your tire pressure, check all your fluids, adjust your valve, clean your injectors, and roll up your windows when you drive for aero dynamics
I did some of these things and now i get 25 city and 30 freeway. NO LIE. 270-310 mpg depends on my driving habits. good luck =) oh yeah my only mod is a cai.