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Estimate Gas Consumed versus Pumped

Discussion in 'Gen 2 Prius Fuel Economy' started by mtc1234, Mar 30, 2005.

  1. mtc1234

    mtc1234 New Member

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    I pumpted my first tank yesterday. The vehicle is great, and I am quite pleased. I'm tracking all the numbers that I can think of (at least for awhile). I've seen many posts about the differences between MFD MPG and calculated MPG. It seems that there's often a difference, but with respect to lifetime it's not too far off.

    I was interested in comments on the following scenario. I took the MFD Miles and divided by the MFD MPG to come up with "Estimated Gas Consumed". This number I directly compare to the amount I pumpt into the system. In the long run, I'd expect these numbers to be close, or at least consistently spaced. Yesterday, I calculated 8.5, but pumped 9.4. If the numbers were reversed I would feel better. I'll have to see in a couple of weeks how the next filling goes.

    A separate question: has anyone tracked the number of miles (or gallons) per "box" (i.e. the gas gauge divisions)? I plan on trying to keep an eye on the mileage when the boxes disappear. I'd like to know whether it's linear or not, etc.

    Thanks.
    mtc
     
    #1 mtc1234, Mar 30, 2005
  2. Batavier

    Batavier Member

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    The bars left is not an exact indication how many miles you can still travel on a tank.

    But with three bars left I can usually travel 200 to 300 km before the last bar starts blinking.
    After the blinking I try to fill her up as soon as possible, for it makes me nervous. :) But I have one time driven some 80 kms with a blinking bar and still was able to get 42.5 litres into the tank. I drive a European Prius without the bladder (tank capacity 45 litres). So in theory I still had 2.5 litres left. I really need to install a camera in the tank. :p
     
    #2 Batavier, Mar 30, 2005
  3. DaveinOlyWA

    DaveinOlyWA 3rd Time was Solariffic!!

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    Batavier is right the "boxes" on the fuel gauge are not linear in any way. i tried tracking them and got numbers ranging as little as 15 miles and as much as 160. also the numbers varied wildly for each bar on different tanks.

    on the first fillup for you, your results are dead on. the reason is that you received your car with the tank "full". the biggest reason for the discrepancy is the intrepretation of full. i believe that Toyota officially does not overfill so would only fill the tank to the first stop without any topping off.

    also because of the bladder you will most likely find that the "mfd mileage" will alternate between being over and under the calculated "pump mileage" because its tougher to get the same fill level and although many people talk about it, i strongly recommend that you do not fill "till you see gas in the filler neck".

    in my sig line you can see that eventually the numbers start to merge. in fact if i ignore the first fillup i had, the difference after 25 filllups is only .4 gallons. but i attribute the merging of the numbers in the fact that i stopped going more than a few cents past the first stop anymore.
     
    #3 DaveinOlyWA, Mar 30, 2005
  4. jimofdg

    jimofdg New Member

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    I used to add just a bit more gas, to reach an even $.05 for my convenience. Now I find myself just letting the pump shut off and call it a day. For a brief time as I first owned the Prius, I would add just a bit of gas so the GALLONS would end in as few decimal places as possible. Too compulsive. I took a cue from the Prius odometer, which displays no tenths of a mile (unless you want to use the trip odometers).

    Remember, no flash photography!
     
    #4 jimofdg, Mar 30, 2005
  5. john1701a

    john1701a Prius Guru

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    It is "BLADDER EFFECT" season. The arrival of Spring (warmer temperatures) is causing the bladder to relax, which causes the capacity of the tank to increase.

    So it is completely normal for a "more than expected" fill to occur during the transition from Winter.
     
    #5 john1701a, Mar 30, 2005
  6. SB

    SB New Member

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    I noticed today that on my 2005 Prius, that although I thought the gas tank was full, only 9
    bars on the gas gauge were lit up. So as an experiment, I went to the gas station and
    made sure that the tank was completely full. It still only indicates 9 bars out of 10. The
    Toyota dealer says the gauge may need recalibration. Anyone else had this problem? I have had the car for 3 weeks, and today is the first time that this has occurred.
     
    #6 SB, Apr 3, 2005
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