It's worth noting also that he's not talking about "driving in hilly terrain", the original comment is talking about driving almost exclusively uphill. Going to Tahoe you'd go from somewhere around 0ft to around 8500ft depending on the pass, and then down only to 6200ft.

Of course, this will impact all cars, though I find only a few MPG difference in our vehicles driving up to the ski resorts around Tahoe.

One curious thing I've noticed is that my relatively-high-Torque-and-HP car with a manual transmission gets almost the same mileage on flat ground versus going up and down mountain ranges, assuming there's no net elevation gain.

My girlfriend's fairly underpowered Subaru with a 4 speed automatic does significantly worse in the hills than it does on flat ground.

Also interestingly, the Tesla should get significantly better mileage in thinner air (on flat ground) where a gas-engined car has to deal with less air to burn which balances out the lower wind resistance.

Would also be interesting to see how the elevation change would affect a tesla at net 0. Say, drive from Sacramento to Truckee and back; I think the range should be plenty.