It might be best to add changes in elevation? So, maybe do that same test in both directions? Then maybe a bunch of times? So, it's a LOT of work unless it happens to match someone's normal daily travels, someone who is also willing to the extra work on a regular basis, which is probably a lot less fun than it sounds. The few test runs I did surprised me, coming from lore in the Volt forum on such matters, I thought by definition that using the gas generator as part of an energy cost driving routine would be terribly inefficient and relatively high cost. The data I got was barely above anecdotal, but surprisingly good, still some loss by the extra conversion, but no where near as lossy as I expected. Beyond just playing by pushing buttons (sometimes unnecessarily, which I enjoy way too much), I think the only time I've somewhat seriously used hv charge is when I left the rest stop on the thruway and forgot to push hv. That seems to be a common thread problem [hello HONDA if you are listening ], not sure what the fix is beyond @insightman 's sticky reminder. Maybe there could be a way to change the default to start in hv for highway trips, but then you have to remember to set it back to EV. Or, above 60 mph for more than 5 minutes Siri, Alexa, (or equivalent), could come on and say, "You seem to be driving on a highway, would you like to save your EV miles for around town, and switch to hv now?"