calculated vs. computer MPG - Please post your results

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

  1. Sarp1028

    Sarp1028 Junior Member

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    FCD: 42.7
    Hand: 39.7
    Difference: 3 MPG or ~ 7.5% too high :-/.
     
  2. CajunKens2014Pv

    CajunKens2014Pv Junior Member

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    FCD: 50.2
    Hand: 48.8
    Difference: UNACCPETABLE! 8O Fix it!
     
  3. ETP

    ETP 2019Prius(Limited),Highlander HYB Plat,B52-D,G,F,H

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    3 ish for me. Of course it depends on how accurate the gas pump is. I suspect you never get a full gallon at the pump but just a little shy so as to meet state regulations. No business model will give you more then what you paid for. Prius comes real close.
     
  4. 70AARCUDA

    70AARCUDA Active Member

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    ...agreed, the VEHICLE gives "full measure" (mpg), it's just the dash instrumentation that's "fudging" its values.
     
  5. Salamander_King

    Salamander_King Senior Member

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    I have been diligent on keeping record of millage on my cars. My 2015 Prius now on 12K mile always shows higher mpg than hand calculated in the range of 5-10%. The last fill up was 49mpg by hand and 54mpg by dashboard. My previous car was 2008 Civic hybrid and it actually showed less mpg on the dashboard than the hand calculated.
     
  6. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Same experience here, coming from 06 Civic Hybrid.
     
    Salamander_King likes this.
  7. ETP

    ETP 2019Prius(Limited),Highlander HYB Plat,B52-D,G,F,H

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    2003 Civic Hybrid was way off. 7 mpg in the wrong direction.
    2007 Civic Hybrid was lemon lawed for piston slap.
    Last Civic had suspension problems and drivers door window.
    Have not had a single issue with my 3 Prius's.

    2004 Civic was the best of the bad bunch.

    I may consider a Leaf if I move to the city when I retire. Just like the Prius and the quality build and how it drives.
     
    #1167 ETP, Nov 11, 2015
    Last edited: Nov 11, 2015
  8. Rick Knowlton

    Rick Knowlton New Member

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    3-4 mpg high vs real world. Only 2,300 miles, but my avg. is 49.26 vs car at 52.1
     
  9. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Terfidia, the thing with this thread is to post your calculated mileage (say for a tank), vs what the trip meter is saying.
     
  10. 70AARCUDA

    70AARCUDA Active Member

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    EUREKA!

    I believe the *reason* behind our Prius MID fuel economy being consistently 5% high has been documented (see pages 16-thru-18) in this recent (2014) HEM Data slide presentation:

    http://www.cert.ucr.edu/events/pems2014/liveagenda/24walter.pdf

    ...quoted from page 18:

    Conclusions from Prius Testing
    • Fuel injector data agrees well with fuel tank after 30 gal of fuel added
    • MAF based results show 5% higher fuel economy than fuel tank & injectors
    • MAF based data correlates with instrument panel display
    • So instrument cluster MPG is 5% high


    Source: PEMS Conference 2014 - Fuel Economy Data, Rick Walter, P.E., HEM Data Corp., 2014.

    ...and, here is a link to the HEM Data Corp. website (no affiliation): Fuel Economy Using OBD | HEM Data
     
    #1170 70AARCUDA, Jan 10, 2016
    Last edited: Jan 10, 2016
  11. fazibazi

    fazibazi Junior Member

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    My first usage of Auris HSD. Sorry for my english (I'm form Polnad and i do my best):
    AT my yesterday's (first) trip to work i've reached 6,1 l/100km petrol from computer it's 6,34 from calculation with the fuel tank - im satisfied (400km both sides with 240km of highway and rest of mixed outside roads and city). Tyre pressure 40psi Nokian Weatherproof 205/50/17.
    I will instal in it an LPG instalation (STAG Qnext) that will give me more comsumption for about 15% than petrol (i think on similar trip to work consumption will be 7,5 l/100km of LPG i will calculate it exact after instalation). The LPG tank will be 630/190 with about 40 liters of real capacity.
     
    #1171 fazibazi, Feb 3, 2016
    Last edited: Feb 4, 2016
  12. FroggyTaco

    FroggyTaco Member

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    Do you have a URL(website/link) describing the LPG product or installation?
     
  13. fazibazi

    fazibazi Junior Member

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    I can't give links here so far. Please try ac stag lpg and the first result will be it. The main driver is QNEXT PLUS (with OBD connection - continous lpg corrections(?) from pertoleum map) and its well prepared for start/stop engines and starts engine on LPG when warm - pertoleum needed only for cold start and.......webasto ;) . From their website you can download all instuctions, schematics etc.

    My today's consumption with 70% of highway 30% city'n suburbs was 5,9 :D at highway i tried to not to exeed 120km/h... i will tank tommorow and i hope it will be 0,2 more than computer - only petroleum so far.
     
    #1173 fazibazi, Feb 4, 2016
    Last edited: Feb 4, 2016
  14. pakitt

    pakitt Senior Member

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    Lifetime error tank full to the brink (3 click) about 6% error. First click error, about 3-4%. I assume petrol stations are cheating 0,5-1% and that includes temperature swings that can affect possibly, but not sure how much, fuel volume.
     
  15. PentaTetraContaMiler

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    My 1st test, 2010 Prius III

    FCD: 46.9 MPG
    Hand Calculated: 43.6 MPG
    Manufactured: September 03, 2010
     
  16. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Even with just two or three tanks, the calculation error becomes near nil. Pumping style only effects the calculation of a single tank.
     
  17. kutztown46

    kutztown46 Junior Member

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    We have now owned our 2015 Prius Four for a full year. Here is a graph showing calculated / computer mpg for each tank. We live in eastern Pa. where it gets cold in the winter. My data shows the classic seasonal effect. My average mpg for the year was 51.4 but I averaged 54.6 for the May - September 2015 time period with a best tank of 56.1. My average discrepancy (calculated vs. computer) has been 3.5 mpg, or about 7%.

    upload_2016-2-17_11-31-37.png
     
  18. WyoNewk

    WyoNewk Junior Member

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    Three
    I've had my '15 Prius for 14-15 months and have 35,000 miles on it. I drive quite a bit at 80 mph (Wyoming I-90 speed limit), and while driving around town it often runs all day long including a couple hours sitting still idling so I can charge my phone. (I use my iPhone for my job, taking 200-400 photos per day, many with flash.) Another reason that I leave it running during 10-15 minutes stops is to keep the interior comfortably cool or warm.

    Currently I'm getting around 38-40 mpg hand calculated and 40-42 mpg per display, so the car display is about 5% higher than reality. My salesman told me that the Prius doesn't measure the fuel that's being used, only figures what it "should be" based on the kind of driving I'm doing. I was disappointed when learning that, as my last car with a fuel analyzer, an '88 Saab 9000T, was very accurate and gave me readouts for actual current consumption as well as for the trip or tank.

    My mileage will go up by 6-8 mpg in the summer when it warms up and the snow tires come off.

    I've noticed that head (or side) winds seem to affect the mileage of the Prius much more than they did my F250 psd.

    (Monumental personal post -- my first!)
     
  19. kensiko

    kensiko Member

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    Get one or more powerful powerbank for your phone that would make better sense
     
  20. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Na, run your car to charge your phone, that's the way to go.
     
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