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Constantly showing 43.1MPG average, no matter how fast or slow I drive

Discussion in 'Gen 2 Prius Main Forum' started by ski.dive, Dec 3, 2023.

  1. ski.dive

    ski.dive Active Member

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    My 2008 Prius is Constantly showing 43.1MPG average, no matter how fast or slow I drive.

    If I drive 3 hours on the HWY at 80mph=I get 43.1mpg

    If I drive in the city for 3 hours in stop and go traffic=I get 43.1mpg

    Right after I fill up the gas tank=It shows I get 43.1 mpg

    Is the MPG calculator broken???
     
  2. Tombukt2

    Tombukt2 Senior Member

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    And if you do the math by the gallons you're putting in by the gallons gone after the mileage seen what do you get with real math I'm just curious? Is the car that far off this is on the center display in the consumption screen or something like that right so if you go back to the energy screen do you see your miles per gallon at a given time constantly changing like 1 minute it'll be 90 mi to the gallon and seconds later it'll be 24 and constantly bouncing around while you're driving Is this a fact or not? And then when you go back to the consumption screen where it gives your average miles per gallon I guess that's what that is where it's constantly saying 43.1 you never see that change so when you zero out at Phillip time and you zero out your trip odometers that consumption MPG is now zero and you've reset by pushing reset on the MFD? And now you pump gas usually I'm flashing pip and I'm putting in about 9.7 gallons of gas in our 11.1 rated gas tank and the gas is just started to squirt back at me for the first time I let that settle down few more squirts go in I'm usually sitting at about maybe 10 gallons I've got 436 mi showing on the clock and the last pip is flashing on the gauge. And my mileage or miles per gallon on the MFD is showing like 43.7 44.1 somewhere right in there.
     
  3. bisco

    bisco cookie crumbler

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    That’s a good thing, right?
     
  4. ChapmanF

    ChapmanF Senior Member

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    When was the last time you reset the average? How many miles is it showing the average of?

    10000 miles at 43.1 MPG plus 3 hours on the highway or 3 hours in the city is going to average very close to 43.1 MPG....
     
  5. PriusCamper

    PriusCamper Senior Member

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    There's two different screens that display your MPG... One screen will show MPG in real time and that constantly changes. The other one will show an average that rarely changes. Have you looked at both screens?

    If both screens are locked up then that's something nobody has mentioned before on here. But first step would be to disconnect the 12v battery for a few minutes, which will reboot all the computers to factory settings and fixes most glitches.
     
  6. pasadena_commut

    pasadena_commut Senior Member

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    If the OP never resets the MPG calculation in the appropriate MFD screen it may be showing the lifetime MPG average for the car. If the divisor for that average is 150K miles (or whatever) and the numerator is 3488 gallons (for 43 mpg for that many miles) it absolutely won't matter what the current fuel consumption is, since a few gallons more or less won't change the ratio significantly.

    This does make me wonder how many digits the car uses for storing those values. If the MPG is never reset will one of those counters roll around, giving either 0 mpg or 99.9 mpg? Or maybe they stick at a maximum value, and the MPG will start to mysteriously and ever so slowly rise or fall.
     
  7. Tombukt2

    Tombukt2 Senior Member

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    If you're driving the car like you drive every other car you've owned in other words haven't become a regular Prius driver that most folks can spot a mile away and you're getting 43 one on this older Prius I would be happy and be the last thing I would be discussing probably I could care less about getting it to 50 that will just cost me money. I'm getting 43.1 now and I've made no changes in my life. We will accept that and be ecstatic No problem coming from other vehicles that get in the twenties possibly 30s I'm in good shape. And I'm going to enjoy other things and not worry about can I get to 75 miles to the gallon not at all.