I have had my 09 Fit for a little over a month now. Does anyone know if the in-dash mpg calculations are supposed to be spot on or is there a +/- involved. Mine is only correct about a 1/3 of the time.

 

mine seems to be 10% higher than what i'm actually getting, check the Eco-Fit forum, bet you get some hard numbers there.

 

There are a few threads on this subject. Most users agree that the Honda mpg computer is a little optimistic, usually by 4mpg give or take. The search feature should help you find the other lengthy threads on this subject

 

I find mine to be overestimating by about 10%. It's best to just do it by hand.

 

Thanks for all the replies. It is good to know that I am not alone. I guess I will just do it the old fashioned way.

 

Found it's off about 3-4 miles...if it says 38 mpg, I'm getting 34 mpg.

 

I mentally pull 10% from the figure when calculating the remaining range of the current tank.

EDIT: here's my gas-log since I got the car, complete with what the mpg-meter said about each tank http://www.gassavers.org/garage/viewgaslog/2496

 

There is the usual electronic errors reading the various sensors (injector signals, rpm, etc and there is the fill-up errors because its difficult to fill to exactly the same level every fillup.

You have the best chance if you go at least 200 miles between fillups and zeroing the gage. Short runs of a few miles will lead to huge errors, usually on the high side.