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calculated vs. computer MPG - Please post your results

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

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  1. alfon

    alfon Senior Member

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    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    Trip A : 5,111.5 Miles
    Average Speed: 40 MPH
    Indicated MPG: 54.6
    Calculated MPG: 52.289
    Gal's used: 97.753
    Gas Type: Regular unleaded various brands Costco etc. with 10% Ethanol
     
    #841 alfon, Jul 9, 2012
  2. sunnyd

    sunnyd Junior Member

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    Just filled up and the computer indicated 57.7 MPG when real MPG was 54 MPG. Off by about 6.5%.
     
    #842 sunnyd, Jul 23, 2012
  3. remco

    remco Junior Member

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    #843 remco, Jul 23, 2012
  4. remco

    remco Junior Member

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    GPS will tell you! I have a 2010 III with 40K miles. I noticed the mgp always about 3 % lower than the calculations at fillup. Then I noticed my gps shows me going 57mph and the prius shows 60mph on the highway. I imagine you'd have to check other gps' to see if the prius does really read the mph high. Obviously if it does...there's your error cause. Yes, I have the stock tires. What do you get on a gps for compared speed?
     
    #844 remco, Jul 23, 2012
  5. F8L

    F8L Protecting Habitat & AG Lands

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    The car computer reads correctly despite the speedo being off by 2mph on average. Others have checked odometer accuracy via highway mile markers and the odo appears accurate. :)
     
    #845 F8L, Jul 23, 2012
  6. F8L

    F8L Protecting Habitat & AG Lands

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    Vehicle:
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    Model:
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    07/20/2012
    Miles: 702.5
    Gallons Pumped: 10.171
    MFD = 71.7mpg
    Calculated = 69.1
    MFD vs. Calculated = -2.6
    % Error = 3.8%
    Avg Speed: 37mph
    Price: $3.599
     
    #846 F8L, Jul 23, 2012
  7. alfon

    alfon Senior Member

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    Location:
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    Vehicle:
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    Model:
    III
    Trip A / several fillups
    Miles: 6,136.1
    Indicated MPG: 55.3
    Calculated MPG: 52.863
    Error: 2.437 mpg
    Gals' used: 116.074
    Avg. speed indicated: 40 MPH
    Gas: regular unleaded with 10 % Ethanol (mostly Costco brand)
    Tires: 195x65x15 Michelin Energy Saver AS tires with 44 PSI
    max sidewall pressure in all four tires.

    In theory and I believe in fact, the more miles you have and fillups
    the more accurate you will be on your figures when comparing
    indicated MPG's with calculated MPG's.
     
    #847 alfon, Jul 23, 2012
  8. alfon

    alfon Senior Member

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    Vehicle:
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    Model:
    III
    Trip A (several fillups) without resetting
    Miles: 6417.7
    Avg. speed indicated: 40 MPH
    Indicated MPG: 55.5
    Calculated MPG: 53.0792
    Difference: 2.421

    Gas: regular unleaded with 10 % Ethanol (mostly Costco brand)​
    Tires: 195x65x15 Michelin Energy Saver AS tires with 44 PSI​
    max sidewall pressure in all four tires.​

    ​
     
    #848 alfon, Jul 28, 2012
  9. kalome

    kalome Member

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    Vehicle:
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    Last tank, filled up 07/28

    600.2 miles
    10.38 gallons
    Dash reading 61.2 mpg/manual calc 57.8 mpg = 5.5% error
    Average speed 30 mph
    Constant AC use 75/76 F one to two bar manual setting.

    ​
     
    #849 kalome, Jul 31, 2012
  10. alleyooptroop

    alleyooptroop New Member

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    Hopefully you guys can shed some light on what I'm experiencing. Just bought a package 5 about a month ago. Right now on my current tank the car is showing only 43 mpg! I used trip A to see this info. On trip B (which hasn't been reset since I bought the car) I'm getting 45 mpg. My trips are mostly round trip to work which is about 16 miles. That round trip is about 30% stop and go residential and 70% longer stretches of city driving. I'm almost always in Eco mode and I'm trying my best to apply all the driving techniques I've read about here. There are only 650 total miles on the car so I'm wondering if it's a break in thing? Would appreciate any light being shed on my poor (comparatively) mileage.
     
    #850 alleyooptroop, Aug 6, 2012
  11. F8L

    F8L Protecting Habitat & AG Lands

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    This really isn't the place for this question but yes, it's a break in thing as well a a 17" wheel thing and a new-to-a-GenIII thing. :) all of these combined along with semi-short trips can ding mpg. With decently long trips and some effort you may be able to get into the 50s but a lot of folks average mid-high 40s with 17" wheels unless they have a killer commute, drive slow, hypermile or use 100% gasoline. I would expect your mpg to go up once you figure out the nuances of this car and the tires/car breaks in.
     
    #851 F8L, Aug 7, 2012
  12. alleyooptroop

    alleyooptroop New Member

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    Oops. My apologies for posting in the incorrect thread. Should I start a new thread?
     
    #852 alleyooptroop, Aug 7, 2012
  13. alfon

    alfon Senior Member

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    #853 alfon, Aug 7, 2012
  14. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Location:
    Nebraska
    Vehicle:
    2018 Tesla Model 3
    Model:
    N/A
    Miles: 700.2
    Gallons Pumped: 10.141
    MFD = 72.4 mpg
    Calculated = 69.0
    MFD vs. Calculated = -3.4
    % Error = 4.63%
    Avg Speed: 23 mph
    Price: $3.73
     
    #854 markabele, Aug 9, 2012
    F8L likes this.
  15. kalome

    kalome Member

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    Location:
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    Vehicle:
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    523.4 miles
    9.46 gallons
    58.9 mpg dash reading = 6.1% error
    55.3 mpg calculated
    29 Avg Speed
    3.29 a gallon
    Constant AC use
    Stock 15 inch tires - 42/40
     
    #855 kalome, Aug 9, 2012
  16. F8L

    F8L Protecting Habitat & AG Lands

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    Mark and Kalome, those are nice tanks. Congrats!
     
    #856 F8L, Aug 11, 2012
  17. kalome

    kalome Member

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    Why thank you, but not as good as your numbers.

    I just posted a thread. I would be interested to know how you have yours setup on your Gen III.
    Mounting your scangauge | PriusChat
     
    #857 kalome, Aug 11, 2012
  18. markabele

    markabele owner of PiP, then Leaf, then Model 3

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    Thanks man!

    Off topic, but has there always been this many crazy anti-good-gas-mileage people on this forum? Some of those other threads are nuts.
     
    #858 markabele, Aug 11, 2012
  19. F8L

    F8L Protecting Habitat & AG Lands

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    Everyone's situation is unique so I try to take that into consideration when judging someone's mpg numbers. I know what you are dealing with temperature wise and I think you are doing well so I have to say something. My average numbers are only 64-67mpg indicated because of my uphill commute and higher speeds. If I moved back to my old house my numbers would drop quite a bit. :)
     
    #859 F8L, Aug 11, 2012
  20. F8L

    F8L Protecting Habitat & AG Lands

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    Your ability to pop off 70mpg+ tanks left and right makes me jealous! :)

    The sudden influx of anti-hypermilers is nothing new. When a new model of Prius comes out we see a lot of new members who traded in sports cars for a Prius. They continue to carry their old justifications for speeding and their anger for those who would rather driver slower. I find it amusing that just because they came over from an Acura TL or a BMW We are supposed to be impressed or that maybe they are the better drivers or more courteous because they speed. *rolls eyes*
     
    #860 F8L, Aug 11, 2012
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