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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. Braddles.au

    Braddles.au DEFAnitely using an EBH

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    Location:
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    Vehicle:
    2010 Prius
    Model:
    N/A
    Gen III RHD Australia-delivered, but I've only had it since January 2012 when it had driven 68341km, to which I've added 6500km.
    Difference is settling to 6.5% over 11 tanks.
    Manufacture date May 09

    I also have a Garmin ecoroute HD that reads the OBDCII port. It generally reports slightly higher than the HSI and therefore a bit closer to the tank average. However it can get confused and report a small instantaneous fuel consumption while at the same time reporting that the engine is at 0 RPM.
    It also tracks my fuel purchases on a spreadsheet, so I can enter the true distance, volume and price amounts.
     
    #821 Braddles.au, Jun 9, 2012
  2. alfon

    alfon Senior Member

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    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    Several fillups did not reset Trip "A"

    Miles: 1511.7
    Average Speed: 34 MPH
    Indicated MPG: 55.9
    Calculated MPG: 53.523
    Gal's used: 28.244
    Gauge off: 2.377 MPG
    Gas: Reg/ with 10% Ethanol/ usually Costco Fuel
    Tires: Michelin Energy Saver/ 195x65x15 with 44 PSI (Max. sidewall pressure) in all four tires.
    Miles on vehicle 73,000 plus
     
    #822 alfon, Jun 9, 2012
  3. Hommerun

    Hommerun Junior Member

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    Location:
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    Vehicle:
    Other Non-Hybrid
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    43.4 onboard but 40.8 manual
     
    #823 Hommerun, Jun 18, 2012
  4. F8L

    F8L Protecting Habitat & AG Lands

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    After installing my newest set of tires I decided I am done testing tires and various other components of this new car so I started a real Fuelly for this car. Here are the results from my first tank.

    06/16/2012
    Miles: 524.8
    Gallons Pumped: 8.44
    MFD = 65.3mpg
    Calculated = 62.2mpg
    MFD vs. Calculated = -3.1
    % Error = 5%
    Avg Speed: 43mph
    Price: $3.859/ga

    No AC use despite 95F-107F temps. Tire pressure 40/38psi. 60mph freeway speeds. 90% freeway and some rural road driving. Brand new Michelin Energy Saver A/S tires. 12,700 mile-old oil. :p
     
    #824 F8L, Jun 18, 2012
  5. LTZR1

    LTZR1 Member

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    Vehicle:
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    12,700 miles on FF oil ? Not the best for your engine....for sure ! Might do well to attend to your engine as much as your tires and mileage !
     
    #825 LTZR1, Jun 18, 2012
  6. F8L

    F8L Protecting Habitat & AG Lands

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    Time flies! I meant to bring it in for the 10,000 mile oil change but a few weeks and a few long trips later and here I am. EEK! I just bought the car in March.
     
    #826 F8L, Jun 18, 2012
  7. LTZR1

    LTZR1 Member

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    It sure can. BUT......you did find the time to buy the Ascends.......switch tires with your buddy "the critic"....then buy and mount the new Michelin A/S.........tis your biz for sure......but they all probably took more time than an oil change takes. Last time I checked......engines cost more than tires or gas !

    Would be more than interesting to get a UOA on that oil which would include a TBN, TAN and particle count.
    Willing to bet the particle count would be VERY high.......again.....not the best for your engine.

    Not trying to be a "pain"....but it runs counter to your usual time and attention to tires and mileage.
     
    #827 LTZR1, Jun 18, 2012
  8. SageBrush

    SageBrush Senior Member

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    F8L is just being modest, the extended oil change was ON PURPOSE, in the interests of science. ;)
     
    #828 SageBrush, Jun 18, 2012
    F8L likes this.
  9. alfon

    alfon Senior Member

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    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    Trip to Reno Nevada:
    Filled up in Portland Oregon and upon return filled up
    at same gas station.
    Total Miles: 1,348.6
    gas used: 25.519
    Avg speed indicated: 55 MPH ( freeway speeds 60-70 mph/ ac on 35 % of the time on low setting
    MPG Indicated: 54.9
    MPG Calculated: 52.847
    Cargo: 3 full grown adults with luggage etc.
    Est. gross vehicle weight 3,850 lbs
    Tires: 195x65x15 Michelin Energy Saver Tires with 44 psi in all four tires.
    Oil: 0x20 Toyota Synthetic oil
    Note:
    Route 5 to Rt. 89 in Mt. Shasta CA. to Susanville CA to Reno. Temps from 55 -94 degrees.
    Went to Virgina City, NV and Lake Tahoe, via Mt Rose Highway elevation 8,700 feet
    or so. Trip had lots of mountain passes and we were nearly max loaded.
    I don't know of too many cars that could get this kind of mpg's under
    these conditions etc..

    Our Prius now has over 75,000 miles.
     
    #829 alfon, Jun 20, 2012
  10. alfon

    alfon Senior Member

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    Now trip A which includes the above Trip B

    Total Miles: 3708.0

    Avg. indicated speed: 40 mph

    Gals used. 70.258

    Indicated mpg: 55.0

    Calculated mpg. 52.777

    Who can complain with motorcyle mpg's in a car......
     
    #830 alfon, Jun 20, 2012
  11. F8L

    F8L Protecting Habitat & AG Lands

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    Nice trip, alfon! :)

    Here is my last tank.

    I started off really well with almost 200 miles at 67.7mpg but things went downhill from there. There were a few short trips and then really crazy wind over the last 50+miles. In areas where I should have been at 70mpg instantaneous I was at 50mpg. The wind was THAT bad. I had to fill at a different station than usual which may account for my lower than normal error.

    06/21/2012
    Miles: 594.8
    Gallons Pumped: 9.801
    MFD = 63.3mpg
    Calculated = 60.7mpg
    MFD vs. Calculated = -2.6
    % Error = 4.28
     
    #831 F8L, Jun 22, 2012
  12. SageBrush

    SageBrush Senior Member

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    ^^ A 60+ mpg tank is very nice, but I know the annoyance of watching a great tank plummet. A wind in the opposite direction is a wonderful salve :)
     
    #832 SageBrush, Jun 22, 2012
  13. F8L

    F8L Protecting Habitat & AG Lands

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    I was pretty annoy with it but then realized I would soon turn around and drive home with the wind mostly at my back. Unfortunately it was a shorter trip but I ended it with 73.3mpg, 32.2miles, 50mph avg speed. :) So what I lost on the last tank will contribute to the current tank somewhat. I keep snapping pictures of all these crazy tanks and trips. I'm kind of tripping out on how much better I am doing now than when I first bought the car and how much better it is than my old GenII.
     
    #833 F8L, Jun 22, 2012
  14. SageBrush

    SageBrush Senior Member

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    Get a good night's sleep my friend, for tomorrow you get to endure watching the meter drop from 70 to 69 :D
     
    #834 SageBrush, Jun 22, 2012
  15. F8L

    F8L Protecting Habitat & AG Lands

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    You're so cold blooded! Hahaha
     
    #835 F8L, Jun 22, 2012
  16. alfon

    alfon Senior Member

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    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    Trip B
    Filled at Costco in Warrenton Oregon, slow speed, first auto click and done.
    Round trip to Seattle Washington Pike Place Market. Four persons on board with
    luggage for overnite stay. Vehicle Gross weight, 3,900 lbs.
    Upon return filled up at Costco in Warrenton Oregon, same filling method for accuracy.
    Miles: 388.3
    MPG Indicated: 57.0
    Speed indicated: 44 MPH
    Gals used: 7.086
    Calculated MPG: 54.798

    Trip A which includes above Trip B
    Miles: 4469.7
    Indicated MPG: 54.7
    Speed Indicated: 44 MPH
    Gals used: 85.219
    MPG Calculated: 52.45
     
    #836 alfon, Jun 24, 2012
  17. F8L

    F8L Protecting Habitat & AG Lands

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    Nice! Especially with all the extra gear and people.
     
    #837 F8L, Jun 25, 2012
  18. alfon

    alfon Senior Member

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    Also temps ranged from 50 to 63 or so. Rain was about
    30-40 % of the time.
     
    #838 alfon, Jun 25, 2012
  19. F8L

    F8L Protecting Habitat & AG Lands

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    Adding this tank because the calculated error was abnormally low. I used a different station for this tank of fuel and refueled at my usual station so this could account for the error. I only pumped until the first click at both stations. I will refill at my usual station using the one click method.

    06/25/2012
    Miles: 554.2
    Gallons Pumped: 8.962
    MFD = 62.8mpg
    Calculated = 61.8
    MFD vs. Calculated = -1mpg
    % Error = 1.62
     
    #839 F8L, Jun 25, 2012
  20. alfon

    alfon Senior Member

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    It seems that in summer the mpg dash guage is more accurate than
    in winter. Seems that during winter the gauge is over reading by about 3-3.5 mpg.

    Currently mostly summer weather mpg gauge and calculated is over reading by 2.25 mpg.(see below)

    Trip A which includes above Trip B
    Miles: 4469.7
    Indicated MPG: 54.7
    Speed Indicated: 44 MPH
    Gals used: 85.219
    MPG Calculated: 52.45

    Read more: http://priuschat.com/threads/calculated-vs-computer-mpg-please-post-your-results.65053/page-42#ixzz1z1g1mqcx
     
    #840 alfon, Jun 27, 2012
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