I used to get 39mpg during the first two months after I bought my 2007 HCH. Now, I consistantly get between 51 and 53. I drive the same trip everyday, so my FE is rather consistant. First thing I did was realize that there is no shame in driving slower and less aggressive. Next, I learned how to handle the gas pedal while maintaining my FE meter above 50 when acceleration is not needed.

I am not living in a hilly area, but I know it did shave about 5-10 mpg when I visited family in the hill country...