Gasoline experiment revisited

While using my car for a lot of short trips recently, my gas milage fell below 30 MPG.  This really concerns me because I am still paying nine cents per gallon more than I need to.  I am hoping the MPG will rebound with the change in driving habits back to my regular schedule.  Of course, it could also be damage from the Waldo Canyon fire we had here in Colorado Springs.  Maybe my air filter just needs a good dusting.  I'm going to have to go on line to see where the air filter is and see if I can clean it or replace it on the cheap.