2012 Prius v - poor fuel economy from 0-20 mph

Discussion in 'Prius v Care, Maintenance and Troubleshooting' started by Alpha4, Aug 21, 2021.

  1. Alpha4

    Alpha4 New Member

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    2012 Prius V Five, 90k miles. Starting last week (rather abruptly) I noticed my mpg starting from a dead stop (0) up to 20 mph is pretty bad - showing anywhere from 6-10 mpg on the display. Never seen numbers this low. Once the electric motor kicks in, all is back to normal. Haven't noticed reduced fuel economy at highway speeds. No warning lights on the dash.

    I cleaned the MAF to see if it would help - no improvement. Next will be new spark plugs, as it's probably time according to the manual (still on the original ones - car build date is late 2011). Anything else I should check?

    Also, wondering if it could be the HV battery dying? My hypothesis is that it isn't helping the motor as much from a stop and at lower speeds...but no idea if this is a possibility.
     
    #1 Alpha4, Aug 21, 2021
    Last edited: Aug 21, 2021
  2. Air_Boss

    Air_Boss Senior Member

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    Has the inverter motor generator ECU re-flash TSB been accomplished?
     
    #2 Air_Boss, Aug 21, 2021
  3. bisco

    bisco cookie crumbler

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    not something i have evr paid attention to. i would suggest measring mpg's by the tankful, so your imagination doesn't get the best of you
     
    #3 bisco, Aug 21, 2021
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  4. Alpha4

    Alpha4 New Member

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    No, received the TSB but never took the car in for it. Good thought, as I have heard that others have experienced drop in fuel economy afterwards.
     
    #4 Alpha4, Aug 21, 2021
  5. Alpha4

    Alpha4 New Member

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    Yeah, best not to entirely trust the mpg gauge on the dash. That said, the engine really feels like it is laboring hard from 0-15 mph (it's making that awful droning sound from the engine/transmission that you get when going up a steep hill), so I'm inclined to believe it's burning more fuel too.
     
    #5 Alpha4, Aug 21, 2021
  6. Mendel Leisk

    Mendel Leisk Senior Member

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    Maybe normal? When accelerating your mpg will momentarily dip way down; that’s natural.

    I wouldn’t pay much attention to the moment-by-moment mpg; overall consumption by the tank, calculated, is more important.
     
    #6 Mendel Leisk, Aug 21, 2021
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  7. fuzzy1

    fuzzy1 Senior Member

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    During acceleration, especially at low speed, instantaneous MPG necessarily must be low. And that generally doesn't matter. Figures that matter are your MPGs for a full trip, or round trip, or steady cruising speed after engine warm-up, or between fuel tank refills.
     
    #7 fuzzy1, Aug 21, 2021
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  8. Alpha4

    Alpha4 New Member

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    Absolutely - getting 3,400 lbs of car moving from a dead stop is going to require more energy, no question there. I've owned the car for 8 years and I've never seen instantaneous mpg reading that low, and the engine sounds like it's laboring much harder than usual. As you and others have suggested, I'll keep a log over the next few tanks to see how it plays out. Thanks for the advice!
     
    #8 Alpha4, Aug 22, 2021
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  9. bisco

    bisco cookie crumbler

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    have you cleaned the egr circuit yet?
     
    #9 bisco, Aug 22, 2021
  10. TheLastMojojomo

    TheLastMojojomo Active Member

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    Did anything happen preceding this like a dead 12v or maintenance of some sort?

    Posted via the PriusChat mobile app.
     
    #10 TheLastMojojomo, Aug 22, 2021
  11. sam spade 2

    sam spade 2 Senior Member

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    Yes. He probably accidentally pushed a button so that is shows instantaneous gas mileage instead of average.
    Sounds perfectly normal to me.
     
    #11 sam spade 2, Aug 22, 2021
  12. Air_Boss

    Air_Boss Senior Member

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    We saw no degradation in fuel economy after the reflash. 42mpg before and after.
     
    #12 Air_Boss, Aug 22, 2021
  13. gromittoo

    gromittoo Active Member

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    I am an uber driver, and I reset the avg MPG for every shift. I get pretty poor MPG (for a Prius) because of that fantastically powerful AC unit, and a lot of time idling waiting for passengers to come out.

    I had the reflash done a few months ago, and then did 8 hours of Uber driving. I normally get in the mid 30's, but after the reflash I got into the high 40's (average). Same driving, same AC on. Then it all went back to normal the next day and I refilled the gas tank. I assume the MPG calculation was not accurate for the first tankful after the reflash.
     
    #13 gromittoo, Aug 31, 2021
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