A first for me: on a trip back from visiting my sister & family, was able to sustain 100 mpg for several for extended periods on level, smooth road @ 40ish mph (65ish kph).
This was with the alternator electrically disconnected, and a 20 km/h (12 mph) quartering tailwind.
Of course if you have a gen 1 Insight, this is a piece of cake for you, and you probably don't need the tailwind (or the charge depleting 12v).
MPG for the entire trip was 91.8 / 2.6 L/100 km, using DWL (driving with load), plus engine off coasting where useful. Avg speed was 32 mph, max was 48 on a route that started & ended with sub/urban driving and took me through several small towns with stop signs. Mostly empty rural roads in between.
Bring on more aero mods!