Fuel Gauge

Discussion in 'Gen 2 Prius Main Forum' started by Harper, Nov 9, 2005.

  1. Presto

    Presto Has his homepage set to PC

    Joined:
    Mar 27, 2005
    1,326
    20
    0
    Location:
    Vancouver, BC
    Vehicle:
    2005 Prius

    That is exactly the way for me. I have never run out of gas before the Prius, but it just begs me to keep pushing it to see what fuel economy I can get. It's like a video game that I can't stop plugging quarters into.
     
  2. windstrings

    windstrings Certified Prius Breeder

    Joined:
    Sep 11, 2005
    6,278
    370
    0
    Location:
    Central Texas
    Vehicle:
    2010 Prius
    Model:
    IV

    Here Here!... very well said!... the only thing I would add is I believe its healthy also to expect things may get intense and passionate at times... respect for each other gets questioned as we take personal the challenge of our own ideas and opinions.

    Few of us actually "know" each other out here..... It is always much easier to not take personally "challenges" if the other person implies respect along with that challenge.

    I agree..... most of the conflicts on a forum are not the topics themselves, but rather lack of repect for each other. Everybody has the right to start from a position making statements out of ignorance... thats what the forum is for!....

    Usually its the "new" people to the forum that feel the most threatened.
    But without the "new" people... the forum would die for lack of objective fresh viewpoints.... misinformed or not!
     
  3. herdgirl72

    herdgirl72 New Member

    Joined:
    Aug 22, 2005
    5
    0
    0
    Location:
    Ashland Kentucky
    I have noticed that in the summer the guess gauge is
    a little more accurate than in the fall/winter. I park my
    car outside and this will be my first full winter with my
    Prius so it will be interesting to see how the bladder will
    do in the cold weather. I live in Eastern Kentucky along
    the Ohio River so the average cold temperatures are as low
    as in the upper twenties.

    I usually fill up around 1 bar depending on price.
    If it looks like prices are going up I'll fill up on the lower price
    no matter how many bars I have left.

    BTW, the nighttime temps have been in the 40's and I'm
    averaging 50.0mpg. In the summer months with nighttime
    temps in the 70's I averaged 54.0 mostly in town
    driving under 55 mph.

    I hope this helps someone.
     
  4. Maytrix

    Maytrix New Member

    Joined:
    Aug 22, 2005
    740
    3
    0
    Location:
    Marlborough, Mass
    Vehicle:
    2009 Prius
    Model:
    N/A
    Can't you push the fuel economy, without actually pushing the limits of the gas tank? If you can get 70mpg, and you can actually put 10 gallons in the tank, then anyone that can do the math can figure out you CAN get 700 miles per tank, but why push it?

    As I said, if you go solely by how much fuel you previously filled up with, then you'll never have an issue.
     
  5. Presto

    Presto Has his homepage set to PC

    Joined:
    Mar 27, 2005
    1,326
    20
    0
    Location:
    Vancouver, BC
    Vehicle:
    2005 Prius
    ^^^
    Nah... there is no fun in that. Besides, as I said in an earlier post, I purposely delay fill-ups and put gas in when I can get it for cheaper. Usually, the prices near my church in the outskirts of town are 10c/L cheaper, and if I drive a bit further out it's another 5-10c/L cheaper.
     
  6. airportkid

    airportkid Will Fly For Food

    Joined:
    Sep 2, 2005
    2,191
    538
    0
    Location:
    San Francisco Bay Area CA
    Vehicle:
    2005 Prius
    I got my prius 2,200 miles ago and it's been to the gas station four times so far, each time several miles after the last pip blinks but before any "add fuel" warning illuminates, and each time the intervening travel has been about 510 miles, more or less. I'm a notorious "topper-offer" because I hate cooling my heels at the pump and visit the gas station as little as possible. Topping off adds at least 1 full gallon and as much as 1.75 gallons beyond the vapor return cutoff (particularly with a bladder tank, as the bladder doesn't expand to full limits instantaneously as the fuel fills it up but needs several seconds to stretch out). The additional gallon (to 1.75 gallons) means at least 40 additional miles between gas station visits - closer to 60 - and that's one entire day's commute for me.

    Each fillup (top off) has been from 10.2 to 10.5 gallons, with the average MPG rock solid at 48.5. You'd need a micrometer to measure any finer variance. Of course, that's across about 1,900 miles in a mild climate (San Francisco) and little variance in route (virtually all commute in moderately hilly terain) - increased experience with the car may finally reveal MPG variances due to climate or cross-country route.
    The 48.5 true measure is a mile shy of what the computer claims - not bad accuracy across half a thousand miles if you ask me.

    Miles per pip is probably an impossible measure. The bladder is going to expand or contract with ambient temperature and (unless the sensor somehows measures fuel mass directly) affect the sensor. If the Prius' fuel gauge were analogue, we'd see the needle rise or fall ever so subtly if we sat in the parked car for several hours while the ambient temperature changed and expanded or shrank the bladder. The digital pips mask this effect, but that's why "miles per pip" is never going to work. Each pip is equivalent to some range of miles - and that range will differ for each pip as the nominal contracted shape of the bladder changes as fuel is drawn out of it.

    Anyway, several people have mentioned that topping off is a no-no: what damage am I likely to be doing by topping off? Packing in close to 2 extra gallons is extremely convenient if I can continue to do so.

    Thanks much -

    Mark Baird
    Alameda CA
     
  7. Maytrix

    Maytrix New Member

    Joined:
    Aug 22, 2005
    740
    3
    0
    Location:
    Marlborough, Mass
    Vehicle:
    2009 Prius
    Model:
    N/A
    This seems a bit counter intuituve to me. I don't know about you, but I find that topping off a bit tedious. After auto-shutoff, I can only pump a small bit of fuel at a time. So for me to add 1-1.75 gallons would take a few minutes. Isn't that time spent "cooling your heels at the pump"?

    To spend less time at pumps, I pay by CC, fill up to auto shutoff and take off. If I spent a few extra minutes each time adding an extra gallon or two, I might save myself 1 fillup over a span of 10. Yet, I would have just wasted 10-20 minutes total dealing with topping off. When it only takes 5-10 minutes to fill up, I spend less time at the pump by not filling up.
     
  8. hdrygas

    hdrygas New Member

    Joined:
    May 22, 2004
    3,650
    6
    0
    Location:
    Olympia Wa
    Vehicle:
    2004 Prius
    All I want the auto-shutoff to do is reasonably fill the tank. It does not have to fill the tank but do it to the same level as previously. I have to say I have less problems in summer than winter.
     
  9. FredWB

    FredWB New Member

    Joined:
    Dec 1, 2003
    331
    4
    0
    Location:
    San Diego, Colli-fornya
    So you guys that are filling up before the tank is half empty (or if you're the optimistic type, half full).....are they giving out stamps at gas stations again? Or maybe a prize with each visit? Why would you want to spend so much time at a fuel pump? I mean it's not that pleasant of a place to visit.

    If the Prius tank and gage were more consistant between various vehicles, maybe this would not be such a hot topic. Averaging only 8.2 gallons between fillups and carrying around an extra 3.5 gallons for nothing doesn't sound like it makes much sense. Yet even after the gas tank/gas gage fix was applied that's what I'm stuck with. I want to stay away from my gas station for as long as I can given the advertised gas tank size and mileage. I've learned to put up with what is, for all practical purposes, a 9 gallon gas tank. It sure isn't what the 11.9 gallon gas tank spec implies. Maybe Toyota should just derate it in their specs or something if they have not figured out to make it work yet.
     
  10. windstrings

    windstrings Certified Prius Breeder

    Joined:
    Sep 11, 2005
    6,278
    370
    0
    Location:
    Central Texas
    Vehicle:
    2010 Prius
    Model:
    IV
    Whats this "fix"?... I haven't as of yet heard of this?
    Can you please eleborate?

    Does this imply that "after" the fix there are no problems now with improper venting etc with topping off?
     
  11. engunneer

    engunneer Member

    Joined:
    Mar 14, 2005
    307
    0
    0
    Location:
    Reading, MA
    Vehicle:
    2005 Prius
    Model:
    N/A
    The add fuel warning illuminates at the same time as the pip blinking



    My rule is that if gas prices are rising, then top-off, because it's only a few minutes. If prices are dropping, put in $20 or fill to auto-shutoff (except when the auto shutoff fails!), whichever comes first.

    I tend to fill when one bar is remaining, estimating about 20 miles before it blinks.
     
  12. windstrings

    windstrings Certified Prius Breeder

    Joined:
    Sep 11, 2005
    6,278
    370
    0
    Location:
    Central Texas
    Vehicle:
    2010 Prius
    Model:
    IV

    So it sounds like you do both.... do you notice any improvement or degredation of mileage either way?
     
  13. suemarnold

    suemarnold New Member

    Joined:
    Oct 12, 2005
    8
    0
    0
    Location:
    Mendocino, CA
    Hi all,

    I've had my 2004 Prius for 3 weeks (bought from a family friend with 8000 miles). I've filled the tank twice--the first time at one bar left and it took 7.28 gallons. The second time when it was flashing and it took 7.99 (went 372 miles or 46.55mpg). Not complaining, but I had hoped to go further between refills, but am reluctant to not pay attention to the flashing. Is my experience within the normal range?

    I'm still learning how to use the list (my first post), but already appreciate all the information I've read.

    Sue in SF Bay Area, who thinks Priii are replicating in Berkeley like Tribbles.
     
  14. Frank Hudon

    Frank Hudon Senior Member

    Joined:
    Jan 11, 2004
    4,147
    11
    0
    after 3 Prius I'd say your experience is probably in the normal range. Hot weather more tank capacity cool to cold weather less capacity. The bladder is one of the reason's the car has such a small ecological foot print. If you just fill the car when you get to one bar left you will never have a problem with the Prius and never get stranded because you run out of gas. You made a fine choice in an automobile.
     
  15. Maytrix

    Maytrix New Member

    Joined:
    Aug 22, 2005
    740
    3
    0
    Location:
    Marlborough, Mass
    Vehicle:
    2009 Prius
    Model:
    N/A
    I fill up when it's conveinent. If that's half full or 1/4 full, then so be it. I'd rather take a few minutes when I have the time then have to take a few minutes when I don't.

    I also don't like it getting too low, because you never know what might come up.
     
  16. olends

    olends New Member

    Joined:
    Jan 1, 2004
    214
    1
    0
    Location:
    Clifton Park, NY (near Albany)
    I am a top off kind of person, but not for a particular gallon amount, but simply for a round dollar amount.

    my rules are if i am within 20c of the next dollar i round up to the dollar above that if less then that i round to the next dollar.


    examples

    18.86 -> 20.00

    26.24 -> 27.00
     
  17. engunneer

    engunneer Member

    Joined:
    Mar 14, 2005
    307
    0
    0
    Location:
    Reading, MA
    Vehicle:
    2005 Prius
    Model:
    N/A
    [attachmentid=896]

    There is no apparent correlation in my data.
     
  18. Locke01

    Locke01 New Member

    Joined:
    Sep 30, 2005
    14
    0
    0
    Just an update and an observation.

    My last bar starting to blink at 345 miles (averaging 48.1 mpg). The pump shut off at 7.4 gallons. Very slowing and carefully, I filled it to 10.2 gallons. To get that 2.8 gallons in the tank took a little over 5 minutes to fill. I could barely squeeze the pump. Any harder and it would shut off. Mind you, this is the first time I did this and a little gas poured out of the top.

    I'm pretty sure the tank (bladder) is near capacity now and I'm hopeful that the last bar wont blink until I hit the 420-425 mile mark (assuming I average 48 mpg).

    I'm probably not going to do it again. This is more or less an experiement on my part. If the bladder takes time to fill up like that, then as someone mentioned. I'll assume I have a 9 gallon tank, not an 11.9 gallon tank.
     
  19. windstrings

    windstrings Certified Prius Breeder

    Joined:
    Sep 11, 2005
    6,278
    370
    0
    Location:
    Central Texas
    Vehicle:
    2010 Prius
    Model:
    IV
    This will be a good chance to see if it really affect MPG.. make sure you compare this tank with previous and let us know!
     
  20. windstrings

    windstrings Certified Prius Breeder

    Joined:
    Sep 11, 2005
    6,278
    370
    0
    Location:
    Central Texas
    Vehicle:
    2010 Prius
    Model:
    IV

    Wholly mackeral!... you guys who keep such comprehensive charts ought to get some bucks from toyota for your info... its ashamed you don't

    based on the one you pasted.. I didn't see the timeline and couldn't interpret what I was seeing too well.. maybe you could help... I say 40mpg right next to 67mpg?.... is there an easy way to know which one you topped of verses not?
     
Loading...