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AVG. MPG counter fluctuating like crazy

Discussion in 'Gen 4 Prius Main Forum' started by 2020XLEAWD, Jun 15, 2021.

  1. 2020XLEAWD

    2020XLEAWD Member

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    The main average mpg counter right next to the speedo and odometer started rapidly changing its numbers three days ago. The dealer said it’s normal, and the computer is just doing some self-corrections. They added that if there were errors in the system, there would be a check engine light on the dash. It just seems odd to me. It was a steady number with gradual increases with LRR tires + city driving and decreased snow/winter tires + highway driving. Now it’s just nonsensical and hasn’t "corrected itself.”Anyone experience this?
     
    #1 2020XLEAWD, Jun 15, 2021
  2. FuelMiser

    FuelMiser Senior Member

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    Has it been recently reset? That would reset the number of miles driven, which in turn would cause the avg mpg numbers to fluctuate "wildly" After a significant # of miles have been recorded, the avg mpg will stabilize back to what you've been used to
     
    #2 FuelMiser, Jun 15, 2021
  3. 2020XLEAWD

    2020XLEAWD Member

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    No I’ve never reset it
     
    #3 2020XLEAWD, Jun 15, 2021
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  4. bisco

    bisco cookie crumbler

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    dealers just blowing you off because they can't fix anything without a trouble light, trch stream, code and service manual. maybe a call to toyota if it doesn't settle
     
    #4 bisco, Jun 15, 2021
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  5. Colin Jones

    Colin Jones Member

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    You haven't changed the trip counter mode have you? Different trip counter modes change the fuel consumption display... if you've got it on "single trip" mode the mpg will be for that trip so will switch up and down a lot, as it is the average over a short trip. If it's on odometer, then it's "all time" (since reset) average so will only change a little:

    upload_2021-6-16_13-39-21.png
    upload_2021-6-16_13-39-36.png
     
    #5 Colin Jones, Jun 16, 2021
  6. 2020XLEAWD

    2020XLEAWD Member

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    I’ll investigate this. That button is on the steering wheel so I wonder if it was pressed accidentally.
     
    #6 2020XLEAWD, Jun 16, 2021
  7. Oh4Corolla

    Oh4Corolla Junior Member

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    I’m having the same issue in my 2017 Prius ll. After picking it up from the body shop (front bumper replacement from an accident) I noticed my lifetime mpg was way down, to 50 or 51mpg. I have 74,500 miles and had been around 54.8mpg. Now every time I drive the car, the lifetime mpg fluctuates greatly, from a low of 50.1mpg, up to like 52.9mpg. But my trip meter shows I’m getting 55mpg+
    To clarify, I was in an accident in October and repairs were made. But insurance paid for a cheap aftermarket front bumper that did not fit properly. Body shop just replaced it with an OEM bumper and it took them about 2.5 days. I can’t see them resetting anything for a bumper replacement.
    Very odd.
     
    #7 Oh4Corolla, Feb 11, 2024
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