Fuel Economy Dropping when stopped & engine not running

Discussion in 'Gen 2 Prius Care, Maintenance and Troubleshooting' started by jsabowabo, Dec 16, 2022.

  1. jsabowabo

    jsabowabo New Member

    Joined:
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    2009 Prius
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    Hi Everyone, first post.

    My son's 2009 Prius just had a new to us engine (w/92k) put in. Since getting it back it has a strange issue. I noticed that when stopped and the engine not running, the indicated mpg continues to drop, as if the engine were idling. I confirmed the engine is not running when this happens.

    The only thing that makes the MPG stay constant is putting the car in Park.

    Aside from that it gets great MPG and runs normal. Any ideas?
     
    #1 jsabowabo, Dec 16, 2022
  2. Tombukt2

    Tombukt2 Senior Member

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    I don't think my MPG and my '09 drops with the car sitting still and the gas engine on or off? I don't think I'll look today and getting ready to drive it in a few minutes I'm looking at the miles per gallon where the little regenerative braking bar graph is not the one that shows the battery condition that's constantly changing all the time way too much to even look at hardly either way I don't think my car does it unless the car is moving and there's input from the driver like the gas pedal something or you're up to speed and the cruise is on
     
    #2 Tombukt2, Dec 16, 2022
  3. PriusCamper

    PriusCamper Senior Member

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    Real time MPG calculations are not what you want to pay attention to or worry about. Everything is fine! With a replacement engine this car will last a really long time!
     
    #3 PriusCamper, Dec 16, 2022
  4. jsabowabo

    jsabowabo New Member

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    It's not the realtime MPG that drops. It's the overall MPG that's calculated since the last odometer trip reset. I'll pull up to a light and it will be at 44 mpg. By the time I pull away it's dropped to 43.2. It never used to do that.
     
    #4 jsabowabo, Dec 17, 2022
  5. jsabowabo

    jsabowabo New Member

    Joined:
    Dec 16, 2022
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    Location:
    Georgia
    Vehicle:
    2009 Prius
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    N/A
    Just wanted to report back for anyone that has this problem in the future. I made no changes, but the problem just went away. Just using the car day to day resolved the problem somehow.
     
    #5 jsabowabo, Feb 8, 2023
    bisco likes this.
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