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Erratic/Inaccurate Fuel Gage

Discussion in 'Gen 2 Prius Technical Discussion' started by tcpike, Oct 9, 2007.

  1. tcpike

    tcpike New Member

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    Since purchasing my 2007 Prius, I've had some concerns that the fuel gage doesn't accurately reflect how much fuel is being consumed or how much fuel is in the tank.

    On a recent trip of 158 miles, the fuel gage dropped 4 squares or 1 square per c. 39 miles traveled. I had driven 100 miles and used 2 squares before starting this trip. The car's consumption screen was registering 47 mpg. Before returning from my trip, I filled the tank with 6.7 gallons. The consumption screen registered total miles of 258 since my last fill-up. The average based on the math (miles divided by gallons) is 38 mpg. Quite a discrepancy!

    On my return trip, I traveled the 158 miles and the gage showed "full tank" (all 10 squares) the whole trip! The consumption screen was showing 58-60 mpg. In fact, I'm still driving on that tank of gas (now showing I've driven 179 miles and just today it dropped one square.

    Has any other Prius owner noticed any odd, erratic occurances with their gas gage? (I've got an appointment to take the car into the Prius service person in two days to check this out.) Any comments would be greatly appreciated!
     
    #1 tcpike, Oct 9, 2007
  2. Proco

    Proco Senior Member

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    Do a search for "guess gauge" and all your questions will eventually be answered.
     
    #2 Proco, Oct 9, 2007
  3. tcpike

    tcpike New Member

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    Thanks for pointing out the thread to me, Proco. So, after reading through that thread, I now understand that the fuel bladder can cause the discrepancy in miles per gallon.

    I guess I'm still not sure if this is also the reason for a full tank staying "full" even though I drove 179 miles. One of the responders mentioned sticking the nozzle back into the tank a few moments before closing the gas cap. Do you suppose I can save myself a trip to the mechanics by something so basic? Or is the "stuck full gas tank" another issue?
     
    #3 tcpike, Oct 9, 2007
  4. qbee42

    qbee42 My other car is a boat

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    <div class='quotetop'>QUOTE(tcpike @ Oct 9 2007, 02:21 PM) [snapback]523201[/snapback]</div>
    Like many modern cars, the fuel gauge on the Prius stays at full for a longer than expect number of miles, then starts to drop. I assume the thinking is that a full tank is not a concern, but a low tank better register with some accuracy. Almost all gas gauges cheat on the full side.

    Tom
     
    #4 qbee42, Oct 9, 2007
  5. tcpike

    tcpike New Member

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    Tom, I can understand that to a certain extent. But, to drive 179 miles and still have the tank showing completely full? That seems a little excessive, don't you? I mean, it should've dropped about 4 squares (at least it did on the first half of my trip). Do you recall reading anyone else having this happen? Otherwise, it seems like something peculiar to my car and would like to have a tech look at it.
     
    #5 tcpike, Oct 9, 2007
  6. Proco

    Proco Senior Member

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    <div class='quotetop'>QUOTE(tcpike @ Oct 9 2007, 03:01 PM) [snapback]523224[/snapback]</div>
    This really is fairly normal for the Prius. In the summer I usually get between 125 & 150 miles to the first pip. In the winter, I get less. I would imagine this is a function of how much you fill your tank. I live in NJ and am not allowed to fill the tank myself, so I'm usually filled to the first click or the nearest $0.25 after.

    FWIW, mine gets a little funky on the back end, too. I usually get around 90 on either the third last or second last pip.

    The more you drive the car, the more you'll get used to it and be able to adjust your driving to what the gauge tells you. For example, I've learned that if I have 3 pips left, I can definitely make it work & back (~100 miles) the next day.
     
    #6 Proco, Oct 9, 2007
  7. qbee42

    qbee42 My other car is a boat

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    <div class='quotetop'>QUOTE(tcpike @ Oct 9 2007, 03:01 PM) [snapback]523224[/snapback]</div>
    I can't recall anyone not having this happen in their Prius. It's completely normal. Remember, 179 miles is only about three gallons of gas. You have to get used to the mileage in a Prius.

    Tom
     
    #7 qbee42, Oct 9, 2007
  8. tcpike

    tcpike New Member

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    Thanks to everyone who weighed in on my question/cibcerb. I've also looked through some more threads and have decided that I'm going to cancel my service appointment. This is just another fun learning experience. And, thank god priuschat is here to help all of us newbies! :lol:

    <div class='quotetop'>QUOTE(tcpike @ Oct 9 2007, 03:32 PM) [snapback]523270[/snapback]</div>

    And, that mangled word at the end of my first sentence would be "concern" :lol: Fingers of the wrong keys... :rolleyes:
     
    #8 tcpike, Oct 9, 2007
  9. abq sfr

    abq sfr New Member

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    The guess gauge is inaccurate on both ends. Yesterday I had a blinking pip for 10 miles, drove to Costco and filled it up with 8.5 gallons after clicking the nozzle three times. Unless I have an incredible shrinking fuel bladder the guess gauge is exactly that. I should have been able to go another 150 miles on the last blinking pip.
     
    #9 abq sfr, Oct 9, 2007
  10. richard schumacher

    richard schumacher shortbus driver

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    <div class='quotetop'>QUOTE(abq sfr @ Oct 9 2007, 05:32 PM) [snapback]523327[/snapback]</div>
    Don't try it; you probably won't get that far.
     
    #10 richard schumacher, Oct 9, 2007
  11. dsharp88

    dsharp88 New Member

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    I've only had my Prius a month so I'm not used to this yet. I filled up today with two pips left on the gauge. I was only able to put in 6.9 gallons (about 44 mpg this tank). I thought it was an 11.9 gallon tank. Does that mean I have 5 gallons left on two pips? It can't be. My previous tank, at 53 mpg, took 7.2 gallons with three pips left so I waited for two this time.

    Does everyone pretty much wait for one pip before filling? Or do they wait for a certain mileage, say 400 miles (10 gallons at a conservative 40 mpg)?
     
    #11 dsharp88, Oct 11, 2007
  12. richard schumacher

    richard schumacher shortbus driver

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    Pips is safer. With a Prius only a fool would assume that they can go at least <your favorite distance here> on the most recently fillup merely because they did so once before.
     
    #12 richard schumacher, Oct 11, 2007
  13. JimboJones

    JimboJones New Member

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    <div class='quotetop'>QUOTE(dsharp88 @ Oct 11 2007, 06:56 PM) [snapback]524274[/snapback]</div>
    This reference http://www.autoshop101.com/forms/Hybrid13.pdf
    says that there can be up to 5 liters difference (at 14 F) with the Prius gasoline bladder. So any temperature between 14 F and above can have over a gallon difference in the amount of fuel the bladder holds. This means that it's not a good idea to go by previous distance travelled on a full tank, since the tank capacity is variable according to temperature. Perhaps if you have consistent weather, and you fill up with the temperature within only a few degrees of the previous fill up...
     
    #13 JimboJones, Oct 11, 2007
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