How accurate is the MFD Average MPG?

it's a bit optimistic. at the pump, that will translate to around 50-51 mpg. the '04 thru '09 has a rubber bladder inside the gas tank, and every fill up is a bit different. best way to get a good average is over multiple fill ups, the more the better.

 

Seems about right to me. I calculate the tank mileage with the gallons I just put in.

Last fill up comes to 9 gals after 1click.

 

that's pretty dang good!

 

I think it's pretty accurate... especially if u have stockISH tires on it. Way to go!

 

but that's a gen 3 display and your avg MPH is only 18 over 500 miles? you must never leave your neighborhood or go on a highway...

 

Mine is off by less than 0.5% on average. I have the European module without gas bladder so no tank has been off by more than 1 l or 0.23 gal. That inaccuracy is mostly due to differences in fuel pumps.

 

I've always tracked my milage from tank fill to tank fill (odo/gals filled) with all my cars.
I have an '04 now, and the MFD estimate has always been within about 0.3 mpg of my tank to tank results.

 

On my 3rd gen the error is 7.5%.

 

Note that several responders in this thread have Gen3s. The typical accuracy seemed to change from Gen2 to Gen3, becoming more 'optimistic'. So when you see impressive Gen3 displays, keep in mind that the displayed gain is composed of two components. Part is a real mpg gain and part is an increased dose of 'optimism'.

 

I didn't specify it was optimistic. How'd you know?

 

I have an old 2004 Prius. I usually get 50 MPG on the MFD but the display is usually 2-4 MPG low.

I was getting 45 MPG this spring, (from 36 MPG this winter) and after a long trip from Muskegon, MI to St Louis,MO and back, the old Prius got out of its funk of low MPG's to normal 50 MPG's. (At 70 MPH)

I think you have to drive a Prius hard to keep it in tune!