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Using www.fueleconomy.gov to store tank info?

Discussion in 'Gen 2 Prius Fuel Economy' started by abq sfr, Jul 15, 2008.

  1. abq sfr

    abq sfr New Member

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    I went to Fuel Economy to find out the EPA estimates for the Prius, it looks like they have a more versatile economy database than greenhybrid. I never remember to enter my tanks at greenhybrid so they are all mixed up because you can't enter the date. The Fuel Economy database has a lot more info you can put in, and will import from an Excel spreadsheet. It looks like only 130 '07 Prius owners have put in data, so maybe it's new? They also have a lot of other interesting data for most cars. Of course, many of us are leery of anything provided by the US Gov't :confused:
    Here's their fact sheet... http://www.fueleconomy.gov/feg/FE_Fact_Sheet.pdf
     
    #1 abq sfr, Jul 15, 2008
  2. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I'll upload my spreadsheet when I have the time.
     
    #2 TonyPSchaefer, Jul 15, 2008
  3. sleonardelli

    sleonardelli Junior Member

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    Just uploaded mine. I'm getting slightly lower than shared data.
     
    #3 sleonardelli, Jul 15, 2008
  4. jammin012

    jammin012 The man behind The Man

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    been logging since 07
     
    #4 jammin012, Jul 15, 2008
  5. Ichiro

    Ichiro Member

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    Bleah... too much work to modify my own spreadsheet and upload it. But, it seems like a surprisingly useful site from the Feds!
     
    #5 Ichiro, Jul 15, 2008
  6. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    Don't edit your spreadsheet. Download their template and cross-reference. That's what I did. Easy sneezy! But their software doesn't like formulas so you'll have to do a "copy/paste special" and select "values" to replace all the references with actual numbers. From beginning to end it took me about five minutes, tops.

    Here's my chart:
    [​IMG]

    It's a bit of a shame that they don't show the years along the bottom. But I guess it really doesn't matter.
     
    #6 TonyPSchaefer, Jul 15, 2008
  7. abq sfr

    abq sfr New Member

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    They should assign names like the Borg... maybe you're 56 of 137?
     
    #7 abq sfr, Jul 15, 2008
  8. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I just noticed that even if you upload your car's MPG they reclacualte it based on the number of miles driven and the gallons pumped. As we all know, this is an inaccurate way of tracking Prius mileage. I was wondering why my chart was so jumpy. They have me bouncing from 61 to 54 to 64. Then they have me with a few tanks in the 30s! There's a stretch where - according to them - I went 62, 53, 62, 71 ,64 ,51, 58, 63, 47, 62, 41.

    I'm tempted to fake the gallons and/or miles just to make the mileage calcualtions correct.
     
    #8 TonyPSchaefer, Jul 16, 2008
  9. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    I didn't carefully read the highlighted line in the instructions for uploading your mileage records.

    2. Data items (excluding headers) must begin in the following cells.
    Data Item . . . . . . . . . . . . . . . . . . . Cell . . . . . Comment
    Date . . . . . . . . . . . . . . . . . . . . . . . A2 . . . . . . Required
    Odometer Reading / Miles Traveled. . . .B2. . . . . . .Required (see 3 below)
    Gallons. . . . . . . . . . . . . . . . . . . . . .C2. . . . . . . Required
    Fill-up Cost. . . . . . . . . . . . . . . . . . . D2. . . . . . .Optional
    City Driving %. . . . . . . . . . . . . . . . . E2. . . . . . . Optional
    Highway Driving %. . . . . . . . . . . . . . F2. . . . . . . Optional
    MPG. . . . . . . . . . . . . . . . . . . . . . . G2. . . . . . . Optional (will be recalculated)
    Comments. . . . . . . . . . . . . . . . . . . . H2. . . . . . .Optional
     
    #9 TonyPSchaefer, Jul 16, 2008
  10. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    [​IMG]

    That's more like it. And no I don't feel bad because in the end it's the MPG that people are interested in and my graph now properly reflects my MPG.
     
    #10 TonyPSchaefer, Jul 16, 2008
  11. jammin012

    jammin012 The man behind The Man

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    Who says they haven't........
     
    #11 jammin012, Jul 16, 2008
  12. carz89

    carz89 I study nuclear science...

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    Not true. Cumulatively over all your tanks, it is the most accurate method. It can be inaccurate for one tank if you are witness to the gas tank bladder effect. I calculate using both methods for each tank, as well as cumulatively, and I've found that the manual method does vary a little bit more (larger standard deviation), but not unreasonably so. Admittedly, I rarely have the gas tank bladder effect resulting in premature shutoff. Cumulatively, my manual calculation (which is more accurate over time) yields 2 mpg lower than the cumulative MFD-calculated data.
     
    #12 carz89, Jul 17, 2008
  13. TonyPSchaefer

    TonyPSchaefer Your Friendly Moderator
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    You failed to quote my next sentence, which when compared to your sentence is exactly the same thing. Now put that into the context that I have 95 tanks so far. If you would have also quoted another sentence. . .
    . . . you would see that I have no contention with long-term averages, only individual tanks.
     
    #13 TonyPSchaefer, Jul 18, 2008
  14. jammin012

    jammin012 The man behind The Man

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    The car calculates your instant and average MPG based on fuel injector performance irregardless of how much fuel you put in your tank.

    If you go by how much fuel you put in / how far you go you will come up with errant data. If there's a standard deviation then yes eventually you'll reach a true average over time. But with the bladder you're not getting a standard deviation therefore your data is ALWAYS suspect no matter how many data points are entered.

    I'm consistanly 2-3 MPG lower in manual calculation than what the car says. Once in awhile I'll get and outragous number like 57mpg when I know it's more like 47mpg. These outragous high numbers don't make up for the consistantly low calculations.

    I trust what the car says and use the manual calculations as a guesstimate. I haven't tracked what the car's MFD average is, I just reset when I fill up.

    If you can't consistantly fill the tank to same point then your data is and will always be wrong. That's why the car doesn't care how much fuel you put in, just what's running through the injectors. Flowrate/pulse rate, can't beat that math.
     
    #14 jammin012, Jul 19, 2008
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