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Misleading fuel guage near empty

Discussion in 'Gen III 2010+ Prius Technical Discussion' started by cagauss, Apr 10, 2011.

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  1. cagauss

    cagauss Junior Member

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    I have new 2011 Prius IV. Two days ago I drove until guage was flashing for 10-20 miles, and the trip display "miles to gas station" was showing 10.

    I pull into station and fill tank, even with extra squirt after first shutoff. Pump reads 9.9 gallons! Does this mean I have 2 gals left? The manual says tank capacity is 11.9 gals. Should I risk going another 60 miles after guage says 10 miles to go for station? How can I estimate how much usable fuel I have left in a low tank?
  2. F8L

    F8L Protecting Habitat & AG Lands

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    Is it big deal to just get gas when you get the warning light or do you just like to push the limits? :)
  3. airgas1998

    airgas1998 New Member

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    bragging rights of "look ma 600 miles on one tank". i just don't understand the philosophy behind this.:confused:
  4. krelborne

    krelborne New Member

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  5. cagauss

    cagauss Junior Member

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    Reason is I go 450 mi per week regularly and I go out of my way to fill up at COSTCO and I want to do it just once a week.
  6. F8L

    F8L Protecting Habitat & AG Lands

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    Makes sense. :)

    Have you tried any driving techniques or tricks to get better gas mileage? These could help extend your tanks in the event you decide you need to push the limits.
  7. fuzzy1

    fuzzy1 Senior Member

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    Is this any different than your previous vehicles? It is no worse than my three most recent non-hybrids.

    Real life fuel consumption is very highly variable, so fuel gauging and 'distance to empty' must be very conservative, with built in error margin, to avoid serious customer complaints. For an real life example of what happens with insufficient margin, read Don't Run Out of Charge in Your Leaf.
  8. Paradox

    Paradox Prius Enthusiast / Moderator Staff Member

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    Yeah, 9.9 gallons is the average the 3rd Gen Prius will take once the light starts to flash for fuel. Threads about this dating back to soon after the 3rd gen came out and people tested how far they can drive before nearly getting stranded lol.
  9. wesayso

    wesayso Member

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    Hey, is your name Kramer? :D
  10. rehillini

    rehillini Senior Member

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    Just FYI, when the beep sounded and guage started flashing, the miles to empty read 25 miles. I drove 5 more miles on "0" to the gas station. (on my previous '05 Prius, I could drive 35 or so miles after the beep and fill up with 10.4 or so gals).

    Bob
  11. cyclopathic

    cyclopathic Senior Member

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    Just get a gas can.. really
    When I commuted on bike tank was good for 1.5days, you get pretty tired from daily gas stops.
    if you don't have garage to keep gas in, just stop on random gas station and get just enough to reset counter (2gal?) good luck
  12. mad-dog-one

    mad-dog-one Prius Enthusiast

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    It is a big deal when I drive from San Bernardino, CA to Reno, NV on Hwy 395 (approximately 600 miles) and want to avoid paying an excessive price for gas in a remote area, while ensuring a reasonable margin for error. Do I wait in line for expensive gas in Bishop, approximately half way, or do I save time and money by pushing on to cheaper gas and short lines in Reno? The answer depends on fuel efficiency, how much useable gas I actually have in the tank, and the tolerance of my bladder. Knowing the limits, including the peculiar characteristics of the Prius fuel gage, means I won't exceed them.
  13. pakitt

    pakitt Active Member

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    I see this topic is coming up again with new users. I have a similar "issue" and I am looking now here on PC to see if what I get is the same over the planet.

    I usually fuel up 10-20km after I get the beep. Typically, if I remember correctly, the beep comes when "distance to empty" is "0" - not sooner, not later.

    The tank is, like in the US, 45L/11.9gal. On average I fuel up 35L/9.25gal (over 26 fuel ups so far). So this means that I get the beep, *before* I reach 10L/2.64gal.

    Now my problem today is as follows. Today is the last day of school and people are leaving for holiday - so guess what - fuel is at it's max today - about 1.59€/L.
    So I want to wait a better day - likely late tomorrow, Sunday or Tuesday morning (Monday is never good - they raise prices because people tend to fuel up on their way to work, after the weekend - Sunday afternoon/evening is also not good...).
    So - how much fuel I have left?

    I have driven with this tank 766.2km, with an average of 4.7L/100km so far. This means, 4.982L/100km, considering 6% average overestimation for the MFD. So this means that I have consumed so far 38L/10gal. Which yields, 7L/1.85gal left in the tank. Is this correct?

    But then, if I continue on average to consume 4.982L/100km - this means that with what is left in the tank, I can continue to drive 140km/86mi!!!! Is that correct?

    Well, since the "beep" I have driven already at least an additional 40km at least. This means that the "beep" comes in at about 200km/124mi - WTH???
    I understand being conservative - but 200km pre-warning - I mean, even for the US, that's a *lot*.
    If the "distance to empty" is using the 6% overestimation (very likely), then it beeps on average "6% earlier" than it should. Which means it is even worse.

    If I get the beep at 35L used, 10L still in the tank and I have made, like this time, and average of 4.7L/100km - I still have about 212km/131mi before going dry (or 200km/124mi taking the 6% overestimation into account).
    The owner's manual says (page 499) that the 1st beep is at 6L/1.6gal - well, mine then is 4L off (40% off!). Anyway to reset this so that it is somewhat correct??
  14. F8L

    F8L Protecting Habitat & AG Lands

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    Because your tank is fairly small, paying a bit more for gas is not a big deal. Besides, you should be stopping at the Whoa Nelly Deli in Lee Vining and gassing up there while eating some fantastic food. :p
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  15. F8L

    F8L Protecting Habitat & AG Lands

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    I'm sorry I don't have any sympathy for you GenIII folks. Us GenII people have to deal with a bladder tank which means we get less miles out of a tank and there is no way in hell we can know how many miles we have after the light comes on. Somehow we have managed to go on with our lives despite this odd design. :D
  16. billnchristy

    billnchristy Active Member

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    The most I have ever put in was 10.5gal

    I don't see the fuss, when it tells you you're empty you KNOW there is somewhere between 80 and 100+ miles on there, fill up before then and you are gold...even with the 2 gallons mystery reserve you should never get stranded.
  17. F8L

    F8L Protecting Habitat & AG Lands

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    Somehow I got 8ga into my tank once. It's usually never more than 7.5ga and that is running it down to 1 pip for awhile. If I drove around with the light blinking I could probably get 8ga in but that is too risky for my blood. I'd love to be able to fit 10+ga in and not have to worry about the bladder. 500-600 mile tanks would be pretty awesome. :)
  18. oldfolkswagen

    oldfolkswagen New Member

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    I like to live on the edge.
    This afternoon I DID drive 60 miles after the light started to blink, and 40 miles past the ZERO miles to empty. This trip included a 2000 foot elevation pass. When I filled up it took 10.6 gal. -- I guess that I could have pushed it at least 100 miles after the light starts to blink.

    Just my 2ȼ
  19. mad-dog-one

    mad-dog-one Prius Enthusiast

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    Although your description of my bladder is off the mark, I'll give the nellie deli a try, as long as they aren't serving anything caught in that lake. :rolleyes:
  20. bob brown

    bob brown Junior Member

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    They say that you shouldn't top off the tank after shutoff, as it could do some harm. What harm?

    On my old 2004, whenever on a long trip, if I saw a good price on the road, I would slowly squeeze in gas until it was up to the brim. I did several 500 plus miles runs with no problem.
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