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Doing the Math

Discussion in 'Gen 2 Prius Main Forum' started by Mi3ke, May 13, 2005.

  1. Mi3ke

    Mi3ke Junior Member

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    2005 Prius as well
    Vehicle:
    2007 Prius
    Model:
    Five
    My wife reports that when she fills up and figures her milage, it is usually 2 mpg less then what the computer registers. Although this last time the computer was 2 mpg less then the wife's calculations. Anyone have this happen and have an explanation for it? And which number would you trust? Of course I am working under the premise that the wife knows how to do math.

    Cheers, Mi3ke in Albuquerque, home of free parking downtown for Prius'.
     
    #1 Mi3ke, May 13, 2005
  2. DonDNH

    DonDNH Senior Member

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    2016 Prius
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    Four Touring
    Most people find the MFD fairly accurate. What ususally throws off the calculation is the variations in how much gas you put into the tank when you fill up. This amount varies with temprature and how patient you are when the pump automatically shuts off. If you're patient, you can often fit another gallon or so into the tank.

    In the long run, it averages out if you keep track of the miles and gallons for each filling. (See my sig)
     
    #2 DonDNH, May 13, 2005
  3. DanMan32

    DanMan32 Senior Member

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    Well, you will have to use a few tanks to know for sure, as your fill level may not be consistent from tank to tank. Since in 2 tanks the errors cancel each other out, it would seem your MFD is accurate and precise. Mine is getting better, but still after over 40 tanks and 22K miles, the MFD is 1 MPG higher than calculated. Used to be 2 MPG, seems to be getting better.
     
    #3 DanMan32, May 13, 2005
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