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Is the "Total Average" MPG legit?

Discussion in 'Gen 5 Prius Fuel Economy & Prime EV Range' started by Will B, Sep 16, 2024 at 9:52 AM.

  1. Will B

    Will B Active Member

    Joined:
    Aug 22, 2023
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    Location:
    Denver
    Vehicle:
    2023 Prius Prime
    Model:
    XSE Premium
    I've had my PPPXP (Pretty Prius Prime, XSE Premium) for a bit over a year now, upgrading from a 2003 Gen1. I like tracking data and for the Gen1 it was pretty easy. For the Prime tracking EV range is easy, but tracking HV efficiency has been messy. The tank readings I had found included EV miles, so were wildly inaccurate for MPGs. I've resorted to logging the DTE after filling the gas tank as an indicator of how I'm doing. Not great, but at least something.

    While fiddling around this past week I came across the "Total Average" MPG display while in HV mode. I had never seen it before. I guess the previous times I had scrolled by it I was always in EV mode, so it was showing EV efficiency.

    Is that what I hope it is, the cars best estimate of MPGs I'm getting in HV mode? If so, that would be cool, have folk been able to verify its accuracy? My car is showing 66MPG which is way too low to be a combination of EV+HV but seems a bit high to be HV only. The owners manual doesn't go into any detail unfortunately, just calling it "average fuel economy".

    If it is what I hope it is, I can finally start tracking MPGs by tank by using the Total (vs Trip) average and then reset on every refueling.

    BTW, don't laugh too much at the label under the display, I have trouble telling left from right! :)

    will Total Average.jpg
     
    #1 Will B, Sep 16, 2024 at 9:52 AM
  2. BiomedO1

    BiomedO1 Senior Member

    Joined:
    Mar 27, 2021
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    Location:
    SacTown, Ca
    Vehicle:
    2021 Prius Prime
    Model:
    LE
    That's probably closest to being correct as far as OVERALL mpg, EV + HV. Looks like your doing a lot of ICE driving. Mine is around 115, because my commute is a few miles beyond my EV range. My ICE usually fires, warms up, then shuts down at the light, as I enter the parking lot to my facility. If it's still running when I park, I'll let the engine complete it's warming cycle before shutting down. You'll know when the warm-up cycle is complete because the car is stationary and in park. The ECU won't shut-down the ICE until the warming cycle is complete. Once the ICE stops, it's OK to shut-down the car.
    I don't think the car's ECU segregates EV vs ICE operations in their calculations, otherwise Toyota would be able to tell you when you need an oil change (like the GM products) rather than trip a alert every 5K. I know the gen4 can't do that and I doubt they've improved that on the gen5.
    The only way I can track actual ICE is by the miles on a tankful of gas driven, divided by the miles driven. Then use EV/ICE percentage to calculate how much is EV vs ICE. That's about as close as you can get.

    Hope this helps...
     
    #2 BiomedO1, Sep 16, 2024 at 10:45 AM
    Last edited: Sep 16, 2024 at 11:03 AM
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