First time past 80 MPG / 2.9 L/100 km in this car for a round trip...
Absolutely perfect conditions. Hot, calm winds, and no traffic, so I could coast forever. I also had the alternator unplugged for about 10 km of those 80 km.
Average speed is low because there are multiple turns & stops on the route. Average cruising speed was 70-80 km/h = 44-50 mph. Probably closer to 44.