I read years ago that using A/C adds less resistance than driving at highway speeds with the window down. That was with ICE cars. Driving in ECO mode I went about 6 Km farther before ICE came on than with out on same trip by going about 3 Kph. slower and having to pass about 6 fewer cars at slow speed. Speed limit was 90 Kph, and I usually go 4 to 5 faster than that. A/C ECO mode is really efficient. It wasn't really hot, about 5C hotter than inside so that would possibly make a difference, was always blowing cool not cold air. Don't like cold air.