Loss of 6 mpg.

Clean the throttle body, especially the MAF sensor (there's a special cleaner for that). Clean or replace all filters. Check/clean PCV. You may also be due for a tune up. Plugs/wires/dist. cap/rotor, check timing. Also check you don't have a dragging brake/sticking caliper. Last but not least, if you do a lot of highway driving, make sure transmission is going into overdrive. A worn lockup clutch can be keeping you out of OD costing you gas mileage.