Definitely interesting to get a range of reports. My experience was a bit different: Soon after getting the car we took a 500 mile road trip from sea level to 7000 feet and back (through Kings Canyon and Sequoia National Parks). 4 of us plus luggage and a horse saddle in the trunk (longer story
Filled up before starting, used HV exclusively for the first part including 75+ MPH highway and about half the climb until next refuel: miles/gallons gave 43 MPG. The next part (rest of climb and mountain twists in HV mode, steep descent with regeneration in EV mode, then most of the highway drive home in HV til the next fuel stop) also gave 43 MPG. Engine was fairly audible on the steepest parts of the climb, but expected and not really more so than our other cars would be (just sometimes disconnected from the actual pedal position, like our other non-plugin hybrid).It was cool but not cold, and I don't tend to use heat much, so I wonder if that's part of the difference -- although in HV mode there should be some engine waste heat instead of all electric. Was the defroster on much if you know? If you do the reverse drive (presumably ending up at lower elevation than the start this time), it would be interesting to see what MPG you get.