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MFD mpg calculation

Discussion in 'Gen 2 Prius Main Forum' started by gjertsen, Feb 8, 2006.

  1. gjertsen

    gjertsen Junior Member

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    I just filled up for the second time a couple nights ago, so I'm now on my 3rd tank. After filling up the first time, I hit the RESET button on the Consumption screen which reset the mpg and miles travelled. Later I read that this would automatically reset if I put some reasonable amount of gas in the tank. So this time after refilling, I left it alone, and sure enough, within a mile or two the miles on the Consumption screen reset.

    However, when I pressed RESET manually (after the first tank), the mpg also reset, such that for the first 10 miles or so the average mpg on the tank jumped around wildly before converging on something near 50. This is what I would expect to happen, as the law of averages would show convergence as I burned through the tank.

    This time, when I did *not* press RESET manually (and let the car automatically detect the fill-up), the average mpg seems to be leftover from my last tank. Meaning, it's fairly stable right around 50.8 where my last tank was, and even after really sweet stretches in cruise control where I roll along electric only (a lovely feeling, indeed!), it doesn't really change all that much, leading me to believe that it is using data from the last tank in its math. Even though the number of miles to the right of it is only counting the miles driven on this tank.

    Does that make any sense?
     
    #1 gjertsen, Feb 8, 2006
  2. Tom_06

    Tom_06 Active Member

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    Yes, as I have noted in several other threads the Average MPG does NOT reset automatically on the 2006's. It does work for 2004's and 2005's. There is no mention of the change in the manual, it says it will reset automatically.

    If you never press reset, it will be the lifetime MPG of the car.

    - Tom
     
    #2 Tom_06, Feb 8, 2006
  3. gjertsen

    gjertsen Junior Member

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    Thanks. How bizarre...
     
    #3 gjertsen, Feb 8, 2006
  4. ca_gary

    ca_gary Dazed & Confused

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    hmmm - so I was wondering the same thing... and even though it seems that the MPG is retained, when I do the manual calculation after the fill up (I am on my 3rd tank as well), the number is pretty damn close. So either I am not getting over 43 MPG in the last 3 tanks (which begs the question "what am I doing wrong to only get 43" or the math inside the car is doing something else.
     
    #4 ca_gary, Feb 8, 2006
  5. philwojo

    philwojo Member

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    <div class='quotetop'>QUOTE(Tom_06 @ Feb 8 2006, 08:00 AM) [snapback]205631[/snapback]</div>

    I am just trying to make sure I am clear on this, I am a new owner and don't have to fill-up yet, but want to make sure I am keep stats the same way most other people are.

    I understand how to do a manual calculation of MPG and I will do that for each tank, but on the MFD do I need to hit the RESET button when I fill up or not, what are most people doing? This is for a 2006 model.

    If I do hit "reset" is that resetting the "total MPG" then, am I reading this post correctly?

    If I do NOT hit the "reset" button then I am letting the car calculate total MPG over the life of the car, again am I look at this correctly?

    Just trying to get it clear in my mind.

    thanks,
    Phil
     
    #5 philwojo, Apr 26, 2006
  6. kente777

    kente777 New Member

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    <div class='quotetop'>QUOTE(philwojo @ Apr 26 2006, 09:26 AM) [snapback]245471[/snapback]</div>
    Actually, I like it NOT to reset. This way, if I go on a long trip, I can use the MFD to track mileage.

    Ken
     
    #6 kente777, Apr 26, 2006
  7. Jeannie

    Jeannie Proud Prius Granny

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    <div class='quotetop'>QUOTE(kente777 @ Apr 26 2006, 11:51 AM) [snapback]245521[/snapback]</div>
    LOL - it's all a matter of preferences! I'm still on my first tank with about 230 miles, but I know that I intend to hit 'reset' each time. I'll keep track of all of my gas purchases, mileage, $ spent, cost/gallon, etc in an EXCEL spreadsheet - I did it for my last car, and and plotted 'spot' MPG, MPG over 3 fillups, over 5 fillups, over 10 fillups, and lifetime MPG.

    So far, I've been doing short trips to/from work (5 miles each way) and local errands; my MPG so far is just a shade over 44 MPG. I've heard from many people that there seems to be a 'break in' period of around 5000 miles, and that MPG gets better after that.
     
    #7 Jeannie, Apr 27, 2006
  8. Rancid13

    Rancid13 Cool Chick with a Black Prius

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    <div class='quotetop'>QUOTE(Jeannie @ Apr 27 2006, 03:40 PM) [snapback]246335[/snapback]</div>
    I've hit 'reset' every single time I've gotten gas whether it be a full-on fill up or just a couple gallons. :)

    Definitely a matter of preferences! The only thing I do to keep track of mpgs is when I fill up, I print out the receipt and scribble my mpg reading and how many miles was on my tank, then enter that info into my greenhybrid.com database. I don't manually calculate anything, I trust the mfd to be pretty close to whatever the actual mpgs would be. :)
     
    #8 Rancid13, Apr 27, 2006
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