30 @ 80 sounds good to me.
I test drove one of those a few years back while I was in Denver [5000 ft. plus as I was over by Golden]. It seemed to move about just fine. I was unable to get any real world F.E., so have wondered about that since. Thanks for sharing.
Oddly, I lived in Larkspur until recently, and the truck got 1 mpg better up there at 7,000 ft.