I just went to big bear... averaged 44 the whole trip.. going up was around 34mpg... going uphill i was averaging bout 45mph .... freeway averaged 80mph On the way down i stopped by a 7 - 11. A guy in a 4runner asked his other buddy in a 4 runner ... what was your MPG.... he said "7.4 mpg" made me smile... i thought i had it bad going up ~
i made two more trips... round trip average were 44mpg and 43mpg...weather at the top was around 30 degrees..sometimes less.. at the bottom was bout 50degrees.
If you're careful the milage drop shouldn't be too bad since you get to recoup some coming back downhill. I just drove to Vancouver BC from Sacramento and even through snow, sleet, hard rain, and 32F-43F I averaged 50mpg. I luckily didn't have super stron winds though. That seems to kill milage.
From Lincoln (near Sacramento) to Marysville, WA. it took 14hrs. I went to Vancouver a day later so I did not count that part but it was about an additional 2 hours if you do not count waiting to get across the border. Technically I was in New Westminster. The weather was pretty terrible but despite heavy snowing the roads were clear and the car performed perfectly even on used stock tires.
