[kilroypr]

First of all where do you live. IF you live on a big city mileage would always will be worst. Did you changed the tstat?(A cooler tstat means worst mileage, on my 98 after installing the 180degf tstat the mileage per gallon dropped from 19.9 to 18.4). Did you checked the tires pressure, Are U certain the air and fuel filters are clean. Would not hurt cleaning your fuel injectors. If you feel like it take out a spark plug and check the tip color. If is light tan or almost normal they are burning fuel correctly if not then depending on the color is how the fuel/air mixture being developed. Too lean can harm the car(In my case broke a piston on heavy load) if it is too rich then you would be wasting gas. And of course your driving style. IF you are an aggresive driver the mileage would go down.