I have just passed the 500 mile mark on my 2004 prius and the average mileage is 39-40 MPG. About 400 miles are highway with a couple of moderate mountains. The remainder s split between rural and city driving.

Is your car in the database? I don't see it...

Check the following:

Oil is not overflowed.
Tire pressure is at or slightly above recommended.
Trip times are relatively long. 5-15 minute trips will kill you.
Speeds are not rediculously over the limit.

Oil seems fine
Trip time was 6 hours total
Traveling about 75MPH (slower thn in my last car. VW-GTI-VR6 golf)
Tires ride pretty hard but didn't check them.
Running CD player and air conditioner (above freezing in Vermont and we need it!).

I should be at least partially in the Data base. I will add more info soon.

with the a/c i wouldnt say thats that bad at 75 mph...thats about 15 over optimal...