Have you ever driven I-5 south over Dexter pass/Siskyous Mt's? If you have done so
without issue or know about them already then you have been over the most hilly
sections of I-5 between Grass Pants and San Fran. I just went to Yosemite this
March in my air-cooled '81 full westy and easily made those passes at 45 mph (hwy
120 into Yosemite was a different story). I have heard that the 1.6 liter diesel is
underpowered compared to the wasserboxers, but I don't know how it compares to
my air-cooled 2.0 liter. I would just recommend NOT filling the water tank until after
you climb the passes, and to lighten the load as much as possible (don't buy food
until near destination?) so that the van doesn't have to work as hard. I weighed my
van on my way back and it came to 4,350 lbs without water and no passengers -
add about 100 lbs for the water and whatever your passengers weigh. That's a lot of
weight for such a small engine! Have a safe trip, and good luck on the terrain!

Peter