I'm about 2,000 miles overdue for my 70,000 checkup at Honda, and I haven't been driving super-carefully. I run the air conditioner, gun the engine to try to make the light before it turns red, and have a nasty tendency to use engine braking. I still managed to drive 397 miles on 11 1/2 gallons of gas, an average of 34 1/2 miles to the gallon. That's pretty close to the 32/39 miles per gallon listed on the EPA sticker.
My next step is to have my car maintenence done and to see if a new fuel filter, a brake inspection (thank you Dave), and a tire pressure check improve my gas mileage, and then I'll drive another tank with a well-maintained car and careful driving techniques.