Very misleading usage of mpg.
I used to drive a semi that would get over 100 mpg - while going downhill. The engine was still running but the primary source of power was the stored potential energy of altitude.
This 230 mpg Prius uses the same logic - stored electrical energy from being plugged in. Sheesh.
Rich H
The Un-Official Segway Battery FAQ
http://www.spinfoot.com/SegwayBatteryFAQ.html