The GoM is a little slow to adjust.. So, if you do a longer highway trip and then you switch to a cycle that has slower speed city traffic in it, your estimation on the GoM will be low and you'll easily exceed it.. If your GoM is based on slow speed city driving and then you'll go on a higher speed road trip, your GoM numbers will be too high.. It does not instantly adjust.. It takes a full charge or 2 to adjust.
Let me give you one example.. I did a trip from Lakeland to Orlando on the weekend at 70 mph with the AC on and 4 people in the car. When I charged Sunday night, my GoM estimated a 248 mile range on 80% charge.. After 2 weeks of commuting, my GoM estimate at 80% charge was up to 275 mile range at 80%.
Exactly. But why? As was pointed out, it is easy to get a much more accurate estimate of your range after driving a few typical miles on a trip using the actual average consumption displayed and the KwH in the battery. So why not give us the option having the car calculate it?