1. Attachments are working again! Check out this thread for more details and to report any other bugs.

calculated vs. computer MPG - Please post your results

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

  1. chota

    chota Junior Member

    Joined:
    Dec 8, 2009
    50
    1
    3
    Location:
    Denver
    Vehicle:
    2012 Prius
    Model:
    Three
    Where to you find the displayed mpg on a 2012 Prius III? It used to be along side of the trip odo
     
  2. Bawb Hoss

    Bawb Hoss ...... V8 Biker ......

    Joined:
    Feb 22, 2012
    22
    1
    3
    Location:
    P6C 3K2
    Vehicle:
    2011 Prius
    Model:
    Two
    :pop2: "What in the same" ..... Do you mean "What in the name" ???:violin:

    :deadhorse: .... It's DEAD ..... They are VULTURES !!!

    :confused: ..... KINKY is GOOD ..... n'est-ce pas ??? :D

    :cheer2:
     
  3. alfon

    alfon Senior Member

    Joined:
    May 17, 2009
    1,370
    270
    0
    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    Filled up three times did not reset:

    Miles: 1,385.7

    Gal's: 26.614

    Average indicated speed: 37 mph

    MPG Indicated: 54.9

    MPG Calculated: 52.067

    Difference 2.833 mpg

    Tires: Michelin Energy Saver/ 195.65.15/ 44 psi in all four

    Gas: Unleaded Regular with 10% Ethanol

    Temps: 40 - 65 degrees/ roads wet with rain
    at times. Average temp 50 degrees.
     
  4. cycledrum

    cycledrum PSOCSOASP

    Joined:
    Apr 9, 2008
    8,245
    1,202
    0
    Location:
    NorCal
    Vehicle:
    Other Non-Hybrid
    Model:
    N/A
    Only 3.5% CONS gage error -

    27 MPH avg
    57.5 MPG indicated
    55.5 MPG actual
    524.2 trip miles
    9.437 gallons refill 87 pump octane

    Mostly dry
    70% hwy miles at low to high 60's MPH

    30% city with some horrible traffic jams in there
    60s to 70s F weather
    tires stock Goodyear Assurance? (38/36 psi front /rear)
    single occupant driving
    No cargo
     
  5. Codyroo

    Codyroo Senior Member

    Joined:
    Oct 24, 2007
    1,826
    515
    6
    Location:
    Pleasanton, Ca
    Vehicle:
    2010 Prius
    Model:
    IV

    Those 3 heads are "beating a dead horse", which is a phrase that means the issue has been concluded but some people continue to debate the issue. You can beat on a dead horse, but it won't move, it is still dead, no matter how much you beat on it.
     
  6. chota

    chota Junior Member

    Joined:
    Dec 8, 2009
    50
    1
    3
    Location:
    Denver
    Vehicle:
    2012 Prius
    Model:
    Three
    Avg speed 26 mph
    Indicated mpg = 58.2
    Calculated mpg = 56.2

    error = 3.4%

    Is that normal for a 2012 Prius?
     
  7. ChipL

    ChipL Active Member

    Joined:
    Feb 28, 2012
    585
    85
    0
    Location:
    Reston, Va
    Vehicle:
    2012 Prius
    Model:
    Two
    I have had anything from a -3.8 to -7.2% difference.

    My last tank:

    Average speed 24mph

    Indicated mpg = 57.2

    Calculated mpg = 53.1

    Error = -7.2%
     
  8. alfon

    alfon Senior Member

    Joined:
    May 17, 2009
    1,370
    270
    0
    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    If you wish to be 100% consistent in actual and
    computer generated mpg, fill up the tank to the
    top of the neck were you can see standing fuel.

    Drive until you are almost empty. Fill up again
    if possible same pump and fill to the same
    level as the first time.

    Result will be 100 % accurate and you can see the
    true difference in calculated and computer generated
    mpg.

    This is how Wayne Gerdes from Cleanmpg.com does his test....
     
  9. beanmat

    beanmat New Member

    Joined:
    May 5, 2012
    22
    1
    0
    Location:
    New Port Richey Fl.
    Vehicle:
    2003 Prius
    Model:
    One
    I drive a mix. of city and free-way in Tampa Bay area in Florida where gas is now 3.48 a Gal and get about 46-48 from calc. fill-ups and 50-52 on dash board read- out. Still getting used to coasting and breaking. Hope this helps.
     
  10. ChipL

    ChipL Active Member

    Joined:
    Feb 28, 2012
    585
    85
    0
    Location:
    Reston, Va
    Vehicle:
    2012 Prius
    Model:
    Two
    About average from most on Fuelly at least for mpg's. :) As for the cost of gas, lucky you! :( Our gas prices are all over the map in the Northern Virginia area; best is just over $3.71 or so. Closer to $3.85 if you are willing to drive an extra few miles from the $3.90 that many are still showing.
     
  11. Big Steve

    Big Steve ramblin wreck

    Joined:
    Mar 5, 2012
    402
    39
    0
    Location:
    Richmond VA
    Vehicle:
    2012 Prius
    Model:
    Four
    First Chip c'mon down to Richmond --- $3.56 yesterday

    Second - yesterday I got 50.9 calc vs. 54.0 displayed -- variance 6%.
     
  12. rebenson

    rebenson Member

    Joined:
    Apr 12, 2008
    364
    43
    6
    Location:
    Suburb of Chicago
    Vehicle:
    2010 Prius
    Model:
    III
    just filled up with "cheap" fuel in suburb of Chicago (3.93).

    Actual MPG 55.78 - Display - 58.9
     
  13. eliteconcept

    eliteconcept 700 mile club, top tank mpg 69.5

    Joined:
    Aug 18, 2010
    449
    186
    0
    Location:
    Indiana
    Vehicle:
    2022 Prius Prime
    Model:
    Limited
    over 35 fill ups logged 16,000 miles I calculate that my prius reports an MPG 5.87% higher than what I actually calculate out. I image that could just be for variance in how much fuel actually goes back into the tank and when the pump decides to shut off. I always stop at the first click when filling.
     
  14. Solyman

    Solyman New Member

    Joined:
    May 3, 2012
    1
    0
    0
    Location:
    Fort lauderdale fl
    Vehicle:
    2011 Prius
    Model:
    Five


    For a 2011 model 5 .Getting 39 mpg actual while computer states 43 mpg. In South Florida using AC mostly and city driving. Price is at $3.49.
     
  15. Brett.

    Brett. Junior Member

    Joined:
    Mar 15, 2012
    134
    26
    0
    Location:
    NJ
    Vehicle:
    2011 Prius
    Model:
    Two
    Just an update, all my tanks read 2.2 mpg higher on the HSI display, than I get in actual calculations after filling up.
     
  16. Brett.

    Brett. Junior Member

    Joined:
    Mar 15, 2012
    134
    26
    0
    Location:
    NJ
    Vehicle:
    2011 Prius
    Model:
    Two
    IIRC filling vehicles to the brim of the tank neck allows raw fuel to make it's way into the evaporation canister damaging it beyond use. As well, on a hot day if there is no room in the tank or neck for vapor expansion you have a pressurized container under your vehicle which could potentially be a dangerous situation in itself. Hose damage may also result from lack of room for expansion.
     
  17. alfon

    alfon Senior Member

    Joined:
    May 17, 2009
    1,370
    270
    0
    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    did not reset A trip after a few fillups here are the results:

    Miles: 1261.1
    Indicated: 56.0 mpg
    Calculated: 53.870
    Average speed: 34 mph
    gal's used: 23.41
    Gas: 10% Ethanol Regular grade gasoline
     
  18. alfon

    alfon Senior Member

    Joined:
    May 17, 2009
    1,370
    270
    0
    Location:
    seaside, oregon
    Vehicle:
    2010 Prius
    Model:
    III
    One fillup in the above composite: camping trip vehicle
    loaded with three people, 100 lb black lab, and heavy gear:

    Miles: 269.7
    Indicated mpg: 61.8
    Calculated: 60.1
    Avg. speed: 36 mph
    Gal's used: 4.483
    Reg gas 10% Ethanol
     
  19. SageBrush

    SageBrush Senior Member

    Joined:
    Jun 4, 2008
    11,627
    2,531
    8
    Location:
    Southwest Colorado
    Vehicle:
    2012 Prius v wagon
    Model:
    Two
    I avoid this tactic for a couple of reasons:

    1. I don't want an accidental spill
    2. If the carbon trap in inundated with fuel it cannot function to reduce pollution
    3. Repeat wetting of the carbon trap may damage it
    4. Toyota says not to

    As for fuel economy accuracy, I simply calculate after a couple thousand miles of driving. The 'tank-full' to 'tank-full' error is reasonably constant and has an upper bound, so I (as it were) enlarge the tank to decrease the percentage error. Wayne has to give the car back in a day or two; we owners can have the accuracy without the problems.
     
  20. 1945steve

    1945steve Junior Member

    Joined:
    Apr 2, 2012
    68
    18
    0
    Location:
    southern indiana
    Vehicle:
    2012 Prius
    Model:
    Two
    I've followed the discussion for a few months now and finally have a full month of data for my 2012 model 2. My variations between the display has been higher than my calculator from 1.5% to 7.5%, on average, close to 5%. However, when backing into the number of miles "still in the tank", it is always off about two gallons X the calculated average MPG. That is very conservative but I would rather have accuracy. Since I was intentionally trying to gather the data, I always used 10% ethanol and was very careful to complete my fill ups the same way. Can anyone tell me if this is a Toyota software bug or intentional. I attached my spread sheet.
     

    Attached Files: