What do you do on a long journey to keep yourself occupied? Well here's an idea. Test the Average Economy part of your on board computer to see how well it works. Take a photo of it while driving at 70MPH.
I was bored. There was a long downhill coming up so I reset the Average Economy at the top of the downhill and coasted down. I'm driving a Tahoe which is not the best in fuel efficiency. Would you believe that Chevrolet do NOT expect their Tahoe to get better mileage than 99.9 MPG? That's where the calculation (or at least the display stops) so I was unable to determine exactly how fuel efficient I was being by driving downhill.
So how long do you think it will be before GMC realize this mistake and fix it on their cars? With hybrids becoming more and more popular they're going to have to address this. It's really a question of whether or not they know about this bug in their system.