Today we did the same trip; I drove both ways since my husband has a broken foot. Up the mountain averaged about 32 mpg and coming back down averaged about 52, so about 42 mpg overall. That's not bad, considering that this time on the way back I drove faster and worked more to keep up with traffic than I had the time before.
What I'm starting to realize is that this car will do very well on extended drives. Short trips, not as well. Still, this is not any worse mileage than I got in my Prius, overall. I'm a happy camper.