calculated vs. computer MPG - Please post your results

Discussion in 'Gen 3 Prius Fuel Economy' started by F8L, Jul 10, 2009.

  1. fuzzy1

    fuzzy1 Senior Member

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    From the article, it isn't clear to me whether this particular statement is limited to hybrids (including their Silverado), or covers the gamut of vehicles with MPG displays.

    But because it was published in early 2006, it cannot be including the Gen3 Prius.

    At 25k miles, the error in mine is 6.0%. This appears to be typical of Gen3 owners posting here, while Gen2 owners typically report better accuracy.
     
  2. Mendel Leisk

    Mendel Leisk Sand Pounder

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    The Honda Civic Hybrid, second generation, errs on the conservative side: if the in-dash says (for example) 5.0 liters per 100 km, calculated usually turns out to be 4.9~4.8.
     
  3. alfon

    alfon Senior Member

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    I completely agree. My ex-girlfriend had a 2006 Civic Hybrid, and I
    kept accurate records of true and computer generated MPG's.

    Alway the error was on the conversative side. If the mpg guage read 52 MPG; caluclated would be 53-54 MPG.

    Just the opposite of our Prius. Our Prius is off consistently 3-3.5 MPG since day one and now we have 46,000 miles and it is still
    off 3-3.5 mpg's.

    al
     
  4. PETEPRIUS

    PETEPRIUS New Member

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    2010 Toyota Prius IV with Navi

    With close to 675 miles I have noticed the MPG guage is off usually 2-3 MPG in the positive.

    LAST FILL UP COMPUTER CALCULATE WAS 46.7 ACTUAL MPG WAS 43.7

    DOES GAS MILEGAE IMPROVE WITH TIME AND WARMER TEMPERATURES?
     
  5. alfon

    alfon Senior Member

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    Warm temps and dry roads is Prius Heaven.....

    al
     
  6. mainerinexile

    mainerinexile No longer in exile!

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    My calculated mpg averaged 5% lower than the display over the first year. It is pretty typically a 2 mpg difference.
     
  7. OHSTATEBUCKEYE

    OHSTATEBUCKEYE New Member

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    I'm consistently seeing 2MPG less between the computer and hand calculation. I'm running about 55 on the computer and 53 by hand calc.
     
  8. Canard

    Canard Member

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    My understanding is oil is changed every 8000 km in Canada.

    Thanks for the reply - I will monitor the error when compared to other fueling stations.

    -Iain
     
  9. seedypea

    seedypea Junior Member

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    48.9 mpg

    Diusplay averages 2.8 mpg High -

    But this is an average of an average

    seedypea
     
  10. tennisfreak

    tennisfreak New Member

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    Had my Prius for just over a month now and have driven about 1500 miles in it (this includes a long road trip from DFW to houston).

    Last tank of gas mpg figures were this:
    Computer: 49.7 mpg
    Hand: 48.6

    Not too bad I'd say.
     
  11. skruse

    skruse Senior Member

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    With complete records, I consistently earn 50+ mpg for 89k mi. Gasoline will eventually go to $20 gallon ($5 Liter), driving the Prius is great. The problem are the wacko drivers who continue to substitute oil for knowledge, don't care about fuel efficiency and think oil and the road will go on forever with no consequences, and in the process let their egos endanger those around them.
     
  12. srivenkat

    srivenkat Active Member

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    Just refueled mine (Built 09/09) at the same pump/station as the previous time.

    MFD: 53.2 MPG
    Calculated at pump: 49.82
    Difference: ~6%
     
  13. tonyrenier

    tonyrenier I grew up, but it's still red!

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    24,000 miles and I'm consistently 2.1 generous on the MFD vs calc., GPS and Scangauge II. But in almost 2 years of hot and cold weather I'm still at 54.2 cumulative.
    Love it!
     
  14. robby3

    robby3 Member

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    Compared this the first time:

    MFD: 4.8l/100km (49 MPG)
    Calculated at pump: 5.2l/100km (45.23 MPG)
     
  15. pakitt

    pakitt Senior Member

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    A bit on the high side (8%), but if you average among several different tanks at different fuel pumps and consistently fuel up the same way, I suppose you will end up at 6% average, like most report here on PC.
    Thanks for sharing!
     
  16. mite66

    mite66 Junior Member

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    Bought it last november, don't know when it was manufactured.

    Added a PHEV kit in January (that worked on and off since then)

    Date calculated Prius diff.

    2010-12-15 5.49 (43 MPG) 5.1 (46 MPG) +7%
    2011-01-26 3.68 (64 MPG) 3.3 (71 MPG) +11%
    2011-02-16 4.79 (49 MPG) 4.3 (55 MPG) +12%
    2011-03-20 3.07 (77 MPG) 2.7 (87 MPG) +13%
     
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  17. djfnw

    djfnw Junior Member

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    I’ve read through many of these posts and it has answered my question about the accuracy of the computer calculated mpg. The consensus seems to be that the calculated mpg is about 6% higher than the manual calculation. I’ll post my results as I get them.

    This discussion has led me to a new question. How do they calculate the 51 mpg city and 48 mpg highway ratings, that are stated on a new Prius? These are the mileage statements for the 2011 Prius. I hope they don’t get these ratings from the computer calculated mpg.
     
  18. billnchristy

    billnchristy Active Member

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    I am going to imagine they do like mythbusters does and put in a seperate tank and measure the weight, drive it, measure again kind of thing.

    They couldn't use the computer because not all cars have them and that would be quite irresponsible (though it is a gov. entity).
     
  19. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Reminds me of mail-in rebates: Companies rely on customers procrastinating, giving up, losing the paperwork or just plain forgetting.

    Similarly, Toyota sets up the computer to lie about miles per gallon (liters/100km), relying on customers to get tired of calculating: just giving up and bask in the glow of falsely optimistic numbers.

    It would be really nice if they would 'fess up and fix it. If it makes them feel better, skip the 'fess up, just fix it.
     
  20. williebill1939

    williebill1939 New Member

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    Gallons into miles the old fashion way,2011 III first half tank 319.3 mi.5.99 gal.i'm impressed,local and back roads 50/50.
     
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