The Insight has an instataneous MPG display, average MPG trip-meter, and an average lifetime MPG display. As Tony stated the amount of fuel used is calculated from the fuel injection system. The calculations seem to be very accurate and are usually off by no more than +/- one percent based on my experience.

(GIS image)


When the car is sitting at idle the instantanous MPG reads zero (as expected), and the MPG/trip average will start to decrease as well. Alternatly, when coasting down a hill, the instantaneous MPG will max out at 150mpg. If you switch to metric displays zero L/100km.

I agree with Tony, all cars should be equiped with these gadgets.

-Jeff