Interesting test, cool that you did that. I would love to see 80 and 90mph averages, and the actual miles vs wh/mile/jargon. To the other persons point, wonder how much consumption changes when you go above 75mph (where most of my highway driving occurs). Would be a cool chart to have to understand actual range with highway speeds, avg temps and random terrain as that’s harder to control obv.
After 138000+ miles my personal experience is 75 is a great speed. How much different 70 is vs 75 vs 80 not worth worrying about IMHO. Too many variables to conveniently chart and if one could would you sit there referring to those charts?
I just go out and enjoy the drive. If there is a stretch without convenient charging, then by all means slow down; it does make a difference.
Don't drive faster than you can replace that energy by charging.