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What causes overtstated miles to empty ?

Discussion in 'Gen 3 Prius Fuel Economy' started by karl.d, Jan 27, 2019.

  1. karl.d

    karl.d Junior Member

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    2011 Prius 170+K miles. Tank was around half full, filled up tank with 4 odd gals. Nothing out of the ordinary, I do not top off, just let the nozzle do its thing. Outside temp in mid 50s. Miles to empty after a fill up generally a tad under 500. Yesterday it shows 566 miles after a fillup (see image). The highest I have ever seen it is a tad over 500 and that was many years ago.

    Anyone experience anything similar, and if so was this a fluke or a harbinger of things to come?
     

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  2. bisco

    bisco cookie crumbler

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    it is a calculation of past mpg's times gallons sensed in the tank. hopefully, you mpg's have been higher recently.
    have you disconnected the 12v lately?
     
  3. karl.d

    karl.d Junior Member

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    12V battery was replaced a few weeks ago. But since then I've been through a few tanks of gas (1.5K miles) in N. CA I-80 / I-5 areas. No abnormalities on those fillups.
     
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  4. bisco

    bisco cookie crumbler

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    possible the sending unit or whatever is broken or messed up. hopefully just an anomaly.
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Oh lord...

    Maybe just fugedaboutit? Watch your gas gauge:

    upload_2019-1-27_13-42-30.png

    and when it's getting low, fill up?
     
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  6. bisco

    bisco cookie crumbler

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    fill up when getting low, i have to remember that (n)
     
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  7. Grit

    Grit Senior Member

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    I posted mine here before showing 612 mi to empty. It’s super accurate and always on the dot :p
     
  8. karl.d

    karl.d Junior Member

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    Thank you. Some of the rural areas, help can take a little while to arrive, especially when cell phone coverage cuts out. So best to research an unusual observation.
     
  9. jerrymildred

    jerrymildred Senior Member

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    As @bisco said, that number is affected by recent driving history. If you've been getting better gas mileage lately, you should expect the car to guesstimate more range per tank until you prove it wrong, at which point it will reduce its guess. There's no way on God's little green earth that the car can know the future, it just takes a stab at it based on you recent history. The gas gauge is the what you need to use, and most people recommend not letting it get too low, especially if you're not in a gas station dense area.
     
  10. cnc97

    cnc97 Senior Member

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    I have a TopOne OBD Bluetooth dongle. I use the paid version of the Car Scanner app for iPhone. It will read the gas gauge down to about .25 gallon. I drove the car 3 different times down to that .25 gallon. I still ONLY put a max of 10.5 gallon of gas in the car. Your result may not be the same as mine, but I am confident enough in my car to drive it that far.

    I find it entertaining to see if I get gas before or after the range gets to zero. Especially if my wife is in the car when the range remaining is in the single digits.
     
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  11. jerrymildred

    jerrymildred Senior Member

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    I go past zero now and then in the city. At zero, it takes around 8-1/4 gallons to fill it to the first click. It has a 10.6 gallon tank.
     
  12. Grit

    Grit Senior Member

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    I’ll second that, getting 60 to 63 mpg so mine shows low 600s to DTE. Can’t wait for non winter blend.
     
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  13. fuzzy1

    fuzzy1 Senior Member

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    With my ScanGauge-II setup, the fuel gauge X-Gauge is scaled such that the minimum tank level reading displays as 0.7 gallons.

    But note that this is a "fake number" that is an artifact of the car's minimum float reading and the OBDII-port engine monitor's scale factors. ScanGauges of my era accept only an integer number of gallons as tank capacity input, and I don't recall if I put in 11 or 12 gallons. Other users who input a different tank capacity, especially on a different OBDII-port device, may see a different minimum display number.

    I must caution users that it is a "fake number", not a true number of gallons remaining, any "zero" extrapolated on this scale is very likely not aligned with the true zero level of the tank. Drivers wishing to push close to the bottom of the tank should first read the base post of Bob Wilson's thread here: [WARNING] Running out of gas (Gen III) | PriusChat.

    But both my current Prius, and its 2010-II predecessor, clearly have more fuel available below that 0.7 minimum reading. I've driven significantly past it several times, and don't believe I ever put in more than 11.0 gallons. I've never gone for the full 11.9 in Prius.

    Though I did go for the full 15.9 in my Forester, with a backup two gallon can for recovery. But by a stroke of good luck on that test, I wimped out and pulled into a fuel station, only to experience fuel starvation just as I parked at the pump. :D And it really did take 15.9xx gallons to refill.
     
    #13 fuzzy1, Jan 27, 2019
    Last edited: Jan 27, 2019
  14. cnc97

    cnc97 Senior Member

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    And my inclusion to the 600 mile club took 11.808 gallons to refill. So the urge to push the tank to the limit is driver beware. Take a gallon or two with you. Or stay close to a gas station.
     
  15. fuzzy1

    fuzzy1 Senior Member

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    Think I did 619 miles (barely short of 1000 km) on 11 gallons or a bit under. But will have to go back through my fuel log book. The replacement tires don't get the same MPG, though that is excused by their better grip.
     
  16. kc5dlo

    kc5dlo Active Member

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    The miles till empty has never been that accurate for me. When i get to somewhere around 30 miles to empty, the gauge will beep and start flashing and a check of the miles to empty no longer shows a number. A lot of people on this forum have reported being able to go 100 miles when the fuel gauge beeps and starts flashing. I am in the same boat as I have racked up over 90 miles on more than one occasion. I do find the gas gauge is pretty consistent. Each tic of the gas gauge is about 1 gallon of gas watching the gauge while pumping gas. That would also be consistent with the extra 100 miles after the gauge starts blinking if the tank holds 11.9 gallons.
    Most of the time it does not matter as I am usually aware of where my preferred gas stations are. It usually catches me off guard when out of town and not familiar with the area.