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When does the fuel light turn on?

Discussion in 'Gen 3 Prius Main Forum' started by Fireboy, May 5, 2015.

  1. Fireboy

    Fireboy New Member

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    Yes. I believe that is the best thing to do.
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Yup yup. You're tactic to take lower speed, secondary highways is a good plan.
     
    #22 Mendel Leisk, May 5, 2015
    Last edited: May 6, 2015
  3. Sergiospl

    Sergiospl Senior Member

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    New Image101.JPG
    And the Pump click was just before 9 gallons of gas!
     
    #23 Sergiospl, May 5, 2015
    Last edited: May 5, 2015
  4. fuzzy1

    fuzzy1 Senior Member

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    At those speeds, it should be easy to beat your indicated 51.7 and even 60 mpg. I suspect you are trying too hard, and have something wrong in the mix. So, because the car is new to you, trying forgetting mpg for a couple tanks and find out what 'normal' driving will produce. After that, then you can work on pushing it higher.

    And sometime soon, fill out this questionnaire and post it here, to give us more clues for feedback:
    Fuel economy complaints/queries? Please copy, paste & answer these questions, esp. if you're new | PriusChat
     
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  5. JC91006

    JC91006 Senior Member

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    I would just be happy to know my car gets around 50mpg and it runs out of fuel before hitting 600......so I fill up when it gets to 500.
     
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  6. Fireboy

    Fireboy New Member

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    Have you read This Thead Yet? YES

    - What fuel economy are you getting and how are you determining fuel economy? (trip computer or manual calculations)
    51.7 COMPUTER
    - What fuel economy are you expecting and why?
    50+ BECAUSE THAT'S WHAT MOST PEOPLE SAY THEY GET
    - What are the approximate outside air temps?
    BETWEEN 60-85
    - How long are your trips?
    20 MILES OR LESS
    How old is your 12v battery? What is the voltage reading of your 12v battery after sitting over night? (Method Here)
    NEW I HOPE JUST GOT CAR 2 WEEKS AGO
    Have you had your alignment checked? Any pulling or abnormal tire wear?
    NO
    - How much of it is city vs. highway? Roughly what's the average speed in overall and and of each segment? Is there a lot of stop and go driving?
    MODERATE STOP AND GO. MOSTLY ROADS THAT ARE 45 MPH OR LESS
    - What's the terrain like of your drives? (e.g. flat, gentle hills, steep hills, etc.)
    MIX. SOME HILLS GENTLE AND A LITTLE BIT STEEP BUT NOT MOUNTAINOUS
    - What are your tire pressures?
    44PSI ALL
    - Is your oil overfilled? (i.e. above the full mark on the dipstick)
    NO
    - Make, model, year, engine and transmission of previous car? (e.g. 08 Honda Civic Si 2.0L 4 cylinder, manual transmission) What did you actually get on the same trips/commute? (Please give us actual numbers, not EPA ratings.)
    1994 CORVETTE 15MPG ALL THE TIME
    - What region/state are you in? (if you haven't set your location)
    SC
    - How are you trying to drive (e.g. trying to stay in electric only?) and how hard are you braking?
    TRY TO STAY IN EV RANGE, BRAKE EASY
    - What modes are you using, if any? "normal", EV, power, eco?
    POWER MOSTLY DUE TO HILLS
    - Are you "warming up" the ICE (internal combustion engine) by letting it idle after powering on?
    NO

    - Are you driving using D or B mode?
    D
    - HVAC settings? Are you using the heater, AC, auto mode, etc.? If using auto, what temp is it set to?
    A/C ON LOW, CUT IT OFF WHEN I CAN
    - Are you using the factory tires and wheels? If not, please indicate tire make, model and size (e.g. Goodyear Assurance Fuel Max 185/65R15). MICHELIN DEFENDER STOCK 15 INCH SIZE

    - If reporting a mileage drop, did anything significant change on your car (e.g. accident, hit a curb or big pothole throwing off alignment, oil change/other maintenance/repairs, changed tires or wheels, etc.) or your commute?
    NOTHING TO REPORT JUST GOT CAR
     
  7. fuzzy1

    fuzzy1 Senior Member

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    That was quick. Here are the few items that jumped out at me --
    If you mean low fan speed, then OK. If you mean LOW temperature setting, this is the highest energy consumption setting. Try cranking the AC temperature up as high as comfortable for lower energy use, mid-70s would be good. The Prius Gen3 has the most efficient AC system available in a passenger car, at least when it was introduced in early 2009. Setting the temp higher will save energy, unlike in previous cars.

    Unfortunately, this higher AC temperature setting conflicts with turning the AC off but still keeping active ventilation, because the non-AC side of the cycle will crank out unwanted cabin heat. I really wish the Prius heat and AC had separate temperature settings, so I could avoid pushing that temperature setting around so much in marginal AC vs no-AC weather.
    Don't overdo this, it isn't a real electric car. All the EV energy ultimately comes from gasoline, and the extra mechanical -> electrical -> battery chemistry -> electrical -> mechanical conversions extract a toll at each conversion step. You are better off putting the gas engine's mechanical energy directly into immediate propulsion, then managing the vehicle's kinetic energy (or momentum) by gliding with the minimum safe and practical braking.**

    Steady gasoline burning is usually more efficient than EV mode, except at the lowest power levels. Pulse & Glide is even better, IF the gas engine can be allowed to stop spinning in the Glide phase, which can happen only below 46 mph in the Gen3 Liftback. (Other models and vintages have slightly different threshold speeds.) Pulse by burning gasoline, toward the right end of the HSI bar, but still in ECO range, not PWR range. Then glide by shutting the gas off, and letting the HSI bar vanish or hover towards the left side of the EV range, but not over into the CHG range.

    On flat roads, this creates an up-and-down speed pattern (5 to 15 mph spread) that likely conflicts with and is unworkable in heavy traffic, but can work very well on mostly empty roads. It can also be coordinated with the up-and-down of hills (pulse up, glide down), which can still be workable with more traffic.

    Note that gliding is not the same as foot completely off the gas. Keep light pressure on the gas pedal to make the HSI bar disappear. Foot completely off the pedal will cause some synthetic drag, to make the car feel more like traditional cars with some engine braking. This will cause the HSI bar to go left into the CHG range, with some light regeneration. While this does put some energy into the battery, a pure glide is more efficient, just like coasting in Neutral. (Gliding in D is safer and more legal than real Neutral.)
    I'm not sure these are as efficient as the originals, but should be fairly close, and are a better tire overall. Are they new? If so, they may need a few thousand miles to break in before producing their best MPG. But this will be 2 to 3 mpg at best.

    **For safety's sake, don't overdo the 'driving without brakes' idea. The real idea of 'driving without brakes' is to think back to the last time gasoline was burned. Could the current braking have been avoided by burning less gasoline earlier? Or by leaving more space to the next car in front? If so, try to do that next time. Not all braking is avoidable this way, and for safety sake, should not be avoided.
     
    #27 fuzzy1, May 7, 2015
    Last edited: May 7, 2015
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  8. Fireboy

    Fireboy New Member

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    THANKS FUZZY!
    I filled up today with 525 miles on the odometer. 10.9 gallons until first click. If my math is right that's 48.16 mpg. I was hoping to break into the 50's but with my new found knowledge I'm sure I can easily achieve it. Thanks for all of your replies and advice.
     
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  9. bingee3

    bingee3 Active Member

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    Ever run out of gas ? I hate when that happens , and I've heard with a Prius , not good ,,
    I fill up shortly when there are 2 bars showing ,, so I won't be beating any Miles Per Tank full records
     
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  10. fuzzy1

    fuzzy1 Senior Member

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    The first fillup doesn't even count, because you don't know just where the dealer filled it up to, and how the car was operated before you took over. The second fillup you personally perform is the first one that counts.

    Lets us know how it goes from here.
     
  11. fuzzy1

    fuzzy1 Senior Member

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    Here is the definitive post on the HSI display for Pulse & Glide, including a nice graphic. Never mind the Japanese annotation, the important parts are in English: glide question

    BTW, the 38.9 km/l on his display translates to 91 mpg. His group of hypermilers was soon doing even better later, with full tanks exceeding 100 mpg. Many of them have commute conditions nearly ideal for high MPG.
     
    #31 fuzzy1, May 7, 2015
    Last edited: May 8, 2015
  12. AlohaBrewed

    AlohaBrewed New Member

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    I was topping off and my total "miles to empty" read 575. Tires are at F46/R40 (slightly bumpier than off the lot F35/R35 but IDM). Correct me if Im wrong but with a longer history data collection, it can skew your avg's ie: 6month of Driving data collection would have a more linear avg line than 1 weeks worth of driving. I wish my commute was more flat! I have to deal with that Livermore hill and the Altimont pass (Based on the traffic).
     
  13. vthreee

    vthreee Junior Member

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    sigh i've learned this has been one of my disappointments with the prius, the fuel light is that one bar, and when it gets low enough it will make a Beep, once.. then it will flash.

    The Prius is not equpped with an additional light like most other cars. It does not warn you much that you're really low on gas. I've just learned that I need to fill up when i'm close to 1/4 left to go.
     
  14. Mendel Leisk

    Mendel Leisk Senior Member

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    With my parents '58 VW you checked how much gas you had with a stick.
     
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  15. Paul Schenck

    Paul Schenck Active Member

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    A full tank of gas weighs 100 lbs if you climb a hill with a hundred extra lbs does it take more energy?
    Sure it does! So don't Cary extra weight up hill ( on flat level ground extra weight is offset by extra Momentum.
    The Prius has a sweet spot though and if you buy cold gas in the morning at the top of a mountain filling the neck of the gas tank with an extra gallon you can get over 600 miles by the time you get to the beach though you won't have any passengers to see it


    iPhone ?
     
  16. Fireboy

    Fireboy New Member

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    This tank is MY first fill up. 48.2 mpg my area is noticeably more hilly than I ever realized. Now that I'm paying attention to it. Seems like every road is a hill or a long uphill grade. I can't take an alternate route that's any better so I may be stuck with 48-50 mpg.
     
  17. Paul Schenck

    Paul Schenck Active Member

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    Not necessarily, the Prius gets to know its driver and its drives. After major service you'll notice a drop when the battery is disconnected and it re learns your habits.
    Just remember the Prius likes to use its battery and recharge it so keep your speed even up and down those hills and it will love it. The hyper mileage guys use this pulse too. Remember the gasoline engine is efficient if it operates in its sweet spot and the electric motors work to keep it there. I'm still amazed at the efficiency of the algorithms that make this happen for each of us. Enjoy!


    iPhone ?
     
  18. The Electric Me

    The Electric Me Go Speed Go!

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    Sorry, but this is a pet peeve of mine.

    How much warning does anyone need? The Prius has a gauge, with lighted pips. When the LAST ONE starts BLINKING...that's a warning.

    The Prius is also equipped with a screen that displays cruising range, and one with a similar number that displays as Distance To Empty.
    If you want warning? Take them literally. Distance to Empty can mean Distance to Empty, and Cruising Range can mean Cruising Range.
    Even though when I reach zero it has been MY personal experience that often I have nearly two gallons left, I take this as simply a NICE buffer that keeps me from running out of gas and being stranded. BUT for warning just assume....

    When 0 appears on these? You're low on gas.

    Just because The Prius doesn't have a 1990's idiot light that specifically lights up and says "Low Fuel" doesn't mean it isn't giving you SEVERAL comprehensible warnings;

    Most spartan vehicles I have owned simply had a mechanical needle gauge, and maybe that light that would illuminate and give you all the in depth information such as saying "Low Fuel". But what that meant in relationship to the needle that may or may not be stuck was left a huge mystery. Even with that, it was simple...when the needle was pointing at E...it was time for me to fill up. The fact that the idiot light was illuminated for the last 12 miles was really unneeded and redundant to the fact that the gas gauge was pointing towards empty.

    I'll take the auditory beep, the final blinking pip, and Cruising Range and Distance to Empty of The Prius as MUCH greater indicators and warnings that I'm getting low on fuel. If you need more warning than what is provided? Maybe it's time for public transportation.

    Rant Ended.
     
  19. Paul Schenck

    Paul Schenck Active Member

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    Loved the rant!!
    I have run out of gas more time in my Prius than any other car I've owned. Used the last of my battery getting into a station and once called AAA for the two gallons they bring out. I get used to getting over 360 on a tank and when wind or passengers or speed get in the way my wife begins her rant!


    iPhone ?
     
  20. The Electric Me

    The Electric Me Go Speed Go!

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    I should of added that I'm talking the Gen 3, that does NOT have the sometimes problematic gas bladder. Familiar with the fact that Gen 2 owners sometimes have problems and many have personal "rituals" involving filling. I'm thinking the reality MIGHT be different for Gen 2 owners.