my wife drives a nissan and the computer gives an instant fuel economy as well as a long term.

while displaying in the instant mode when you floor it the reading is single digits, when you let off and coast it goes up to 60mpg.

if you display the long term it will give you the average since the last reset. the longer you drive between resetting it the more accurate "average" you will get. if you reset it every 10 minutes you can maniuplate and MPG you want.