Hey Linda-
Welcome to the fold.
I agree with what the others say. DOn't forget that your car may have been sitting idling during transport or at the dealership as other people test drove it, which will significantly impact the mileage. I recall that my first tank would have been an abnormally low ~41mpg if I had included the first 20 miles before I took ownership. ~49 when I excluded those measly 20 miles.
Cheers, and best of luck with the new tanks. I had intended to do the same thing as you and try to run one tank as I had with my old Saturn. Well, I never could bring myself to do it, after the hypermiling bug caught on.
Don't forget to read Tarabell's article on how to best take advantage of your new hybrid:
http://www.cleanmpg.com/forums/artic...h-ii-1306.html