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How accurate/inaccurate is the MPG displayed on the dashboard?

Discussion in 'Newbie Forum' started by Alex_H, Jun 21, 2015.

  1. Alex_H

    Alex_H New Member

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    It seems that Fuelly is a popular tool/website for tracking MPG, but I wonder how accurate/inaccurate the dashboard-displayed MPG is. Has anyone compared MPG estimated by Fuelly and MPG on the dashboard?
     
  2. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah, every tank I reset trip meter, note what the car's telling me, and enter it in my spreadsheet along with the accurately calculated. And enter the (real) data at fuelly. One hundred tanks (~50,000 km) tracked now, and error pretty much steady at 7.5%.

    image.jpg
     
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  3. JimboPalmer

    JimboPalmer Tsar of all the Rushers

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    My gen 2 was about 2% higher than fuelly
    My v is 4% high.
     
    #3 JimboPalmer, Jun 21, 2015
    Last edited: Jun 21, 2015
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  4. Dave14Prius

    Dave14Prius Member

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    After 13000 miles on my 2014, it seems to be about 3 mpg too high, give or take a little each tank.If it shows 55mpg, the hand figured tank using same pump carefully filled up would be 52 mpg.This has happened many times.
     
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    My numbers are similar, albeit percent a bit higher. If I have a tank where the dash says 4.2 (liters/100km) it's invariably 4.5 when calculated.

    That was ONE good thing with our previous Civic Hybrid: if the dash said 4.2, calculated would 4.2, or 4.1 (better) sometimes.

    It would be dead simple for Toyota to fix. It's pathetic, like the guy/gal that keeps BS'ing about something, except everyone knows it, they're only kidding themselves.
     
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  6. JimN

    JimN Let the games begin!

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    I figure my MID is optimistic by 7% on average and varies tank to tank. How full is "full"? A significant amount of gas can still be pumped after the automatic shutoff. Pumping in "a little more" to round the transaction up to an even dollar can make a noticeable difference. An additional 0.2 gallon can knock off 1 mpg.
     
  7. Mendel Leisk

    Mendel Leisk Senior Member

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    Yes, but in a tank or two, it will even out. Calculation errors die out quickly.
     
  8. bisco

    bisco cookie crumbler

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    mine is dead, straight up, on.
     
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  9. Alex_H

    Alex_H New Member

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    Okay, thanks for the feedback! I guess I will start using Fuelly and check how it compares to the car-displayed MPG. I am actually very excited! Based on the dashboard, I got 49MPG, 52MPG, and 61MPG on my most recent three long-ish trips (>50 miles). I hope they are not far off!
     
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  10. srellim234

    srellim234 Senior Member

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    I've found the average displayed on the dash in various cars high, low and spot on so I don't count on them. I track miles on Fuelly for reporting and paying attention to any serious dropoff indicating a mechanical problem but other than that I just drive and refill the tank at 1/3 or 1/4 of a tank left. No chance of running out of fuel that way and I alway have peace of mind as a result.
     
  11. alanfoxmd

    alanfoxmd Junior Member

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  12. bisco

    bisco cookie crumbler

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    same here.
     
  13. CR94

    CR94 Senior Member

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    Mine consistently claims it burns 95.0% as much as it actually burns. That's a long-term, properly weighted average that doesn't move more than a couple of hundredths of a percent with each fill-up.