I'm assuming you did the work. Did you gap the plugs? Like mini-e said, check for loose connections, wires, hoses. If you have the old cap and rotor, you can try putting them back on and see if you get a difference. You lost a little fuel replacing the filter (admittedly, not much). Lastly, your new mpg number is only based on 8.5 gallons, so you may get a rebound with your next fill up.
SuperVX 
Threaded Mode
