I had the chance to have the demo Prius from my dealer for the weekend, so we headed to the Stelvio Pass on the boarder of Austria, Switzerland and Italy. The pass is at 2760m (8970ft) the 2nd highest pass in western Europe. I had heard people say here and on Prius online that the car doesnt perform at all well on mountains. We started at the foot of the Stelvio with a full battery (almost) and the first few kilometers were relatively gentle but the battery went doen to emplty quite quick. But the system still tried to recharge the batteries quiet a bit, both from the motor and from breaking/coasting. We climbed about 5/6 of the way without any problems. The fuel consumption shot to 15 - 20 liters/100km (!) at times and the motor was revving like mad. At the 5/6 point we pulled into a cafe for a drink and to admire the view. Surprisingly (as the battery was almost flat) we were able to drive into and out off the car park in stealth mode! The last part (about 15 hairpin bendsand upto 16% gradient we manaded without any problems, but the motor was definatly lacking power. The "loss" of the battery was noticable. Still the pass was reached and parked for a short while to look around. Next, it was down the other side, and withing a very short time we had 100% green again. The road carried down to a town where we then turned to the Passo del Gavia 2.621m on a very windy narrow road. Same effect, battery "dead" quite quick, but we kept upwith and passed a lot of other traffic. We crossed at least 5 passes over 2000m on sunday and the car performed fantastically. the only problem was we were on 1 block on the fuel guage as we reached the ope of the last pass, and no fuel stations in sight (they tend to close on Sundays in Italy anyhow), but again thanks to the way the prius coasts down hill, and the regen breaking, we got to the bottom and into the next large town and found a pump which took cash (but not credit cards) without using any more fuel. Over 450KM of mountain driving the average was 6.4l/100km. On the return I got 3.9l/100km for about 150Km before joining the motorway and getting a return trip of 4.1l/100km for almost 250km. Very happy with the performance.