How long are your "city" trips?

If your trips in the city are less than 10 minutes, you probably aren't getting the best mileage because your ICE is running most of the time (in order to warm up).

When I drive across town in the morning on the way to my summer job, my commute is 10 minutes. My car gets roughly 28-30mpg because the engine never gets a chance to fully warm up, and the hybrid system generally won't let the car drive in electric only mode unless the gas engine is completely warmed up.

On the other hand, when I drive to my normal job (during the school year), I have to drive 25 minutes on the freeway, and then about 10 minutes in the city. When I drive in the city (after the freeway driving), The car is usually in electric-only mode, and getting 40+ mpg.

I've noticed that since school let out, and my average driving time has gone from 35-40 minutes to 10 minutes, my milage has fell a lot.