How does the estimated range even work...

Discussion in 'Gen 3 Prius Technical Discussion' started by BrickedKeyboard, May 8, 2018.

  1. BrickedKeyboard

    BrickedKeyboard New Member

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    So I just bought a used 2012 with 83k miles. Seemed very clean, well detailed, clean engine bay, one owner and no recorded Carfax red flags. Paid 9500. It drives great.

    So I drove it on the gas from the dealer, probably filled at some point either when the original seller turned it in or during the 3 months it sat at the used vehicle dealer, until it reported just 50 miles of range left.

    Filled it up, but it only took 9 gallons. I even pulled the fill nozzle out after shutoff and added more to top the tank off. Get in the car, and now it says an estimated range of 550 miles.

    9*50 = 450. 450 + 50 = 500. Huh? (I have been getting about 50 mpg, just driving normally, no hypermiling. Very happy it works and this tells me this car's hybrid systems are all in decent working order.)

    Does it normally keep a secret reserve of 3 gallons?
     
  2. ReDave

    ReDave Junior Member

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    Short answer, yes. Toyota, and i think most cars are usually very conservative with the gauges.
    But be careful, it's no fun to run out of gas.

    I've found i get gas more often as i've gotten older, why push it...
     
  3. sam spade 2

    sam spade 2 Member

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    Yes. And all of the indicators tell a similar lie.....trying to save drivers from their own stupidity.
    It doesn't always work.
     
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  4. JimboPalmer

    JimboPalmer Friend to those who want no friends

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    The Gen 2 Prius stranded a fair percentage of it's owners. it had a variable sized bladder as a gas tank and it held different amounts of gas depending on outside temperature. The gauge might not move at all from the first 40 miles to the first 160 miles. When it said empty, you had as few as 8 miles, or as many as 50 miles. None of this had anything to do with what the last tankful did. Owners who depended on reserves or consistency walked a lot. The computer needed 3 gallons to notice you had added more gas, so you walked more than once. Gen 2 owners did not love the gas tank.

    Gen 3 engineers got very conservative, management did not want that many unhappy owners again. (here on PriusChat search for guess gauge)
     
  5. BrickedKeyboard

    BrickedKeyboard New Member

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    Thank you for letting me know the context. Yeah, with this Gen3, it's not that I mind it being conservative, I just feel it is being excessively conservative if it sends me to the gas station thinking I'm empty when I have a quarter tank.

    Especially since a quarter tank on a Prius is an incredible distance...
     
  6. tvpierce

    tvpierce Active Member

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    First off, welcome to PRIUSchat!

    My first piece of advice: don't do this. You run the risk of flooding the evaporative emissions system. When the pump shuts off automatically, stop there.

    My second piece of advice: just ignore the Estimated Range indicator. It's a gimic based on gross estimations. As you've seen, it's not accurate. Treat the prius like you would any other car, and refill the fuel tank based the fuel gauge.
     
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  7. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    How 'bout this: just keep an eye on the gas gauge, and you decide when you want to go to the gas station. Forget about the miles to empty indicator.

    I like to fill up whenever the gauge drops below half, but in my case that's only around once a month, you might want to cut it a little finer, lol.
     
  8. grid

    grid Active Member

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    You should get yours checked, my pip flashes with 25 mi DTE, not 125-150 mi DTE (1/4 tank left).
     
  9. fuzzy1

    fuzzy1 Senior Member

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    No, he has it about right, there is nothing worth having checked. For additional detail, read just the first post of this very long thread:
    [WARNING] Running out of gas (Gen III) | PriusChat
     
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