After nearly five years, finally drove to the Rocky Mountains in my Insight. My 1988 CRX HF did not do well, so I was pleasantly suprized the Insight did not have much of a problem.
On I25, the hills are gradual (relatively), but occasionally considerable in Colorado. People typically drive 75-80mph and I could keep up with them comfortably. There were some long climbs that forced a recalibration. Lower gears and/or driving slower probably could have avoided this.
Hwy 34 into Rocky Mountain National Park is winding and very mountainous. Traffic or severe turns kept my driving to moderate speeds, so there were no recalibrations.
One difference on these two roads - the IMA seemed to charge and discharge differently than at sea level. At times downhill, I simply could not force a charge - was the computer safeguarding the battery? The assist mode seemed to be extended in the mountains - maybe there was some concealed charging.
I25 is relatively flat between Denver and Fort Collins and elevated at about 5,500 feet. The higher altitude seemed to improve the fuel economy, although traffic is too heavy an fast to try hypermiling.
To put it in perspective, I hypermiled a 1988 CRX HF going about 60mph about ten years ago. I made the same trip driving 75mph on the Insight. Got 60mpg both times
. In August I will have to hypermile and see if 75-80mpg can be done.
Still wanted to try the most severe mountain test - westbound on I70 leaving Denver. My 1988 CRX HF could not go faster than 50 mph