What do you think of the way I measure MPG?

Discussion in 'Gen 2 Prius Main Forum' started by Merlock, Jun 7, 2017.

  1. Merlock

    Merlock New Member

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    Every time I fill up, I fill until full, then 1 more click for good measure. For some consistency.

    I then take a picture of the odometer and the reading on the pump.

    I've set up a Google Sheet where I enter the amount of petrol I put in, in litres, and the new odometer reading.

    The sheet works out my MPG for that tank of fuel, by taking the miles difference and the litres used to travel those miles.

    I always fill to full, no part-fills, so it's always complete. And I realise some pumps might click at the end with different tolerances but I figured that won't vary by litres. Maybe just a fraction.

    What do you guys think of that? And is there an app that achieves the same results with just entering 2 numbers?

    **I also enter the cost, but that's just for tracking.

     
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  2. bisco

    bisco cookie crumbler

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    i like it.(y) i'm still doing it with pen and paper at the pump.(n)
     
  3. ePWR

    ePWR Member

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    I just look at the little number on the dashboard. Anything over 20 is excellent! :)
    Just drive it.
     
  4. srellim234

    srellim234 Senior Member

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    It's okay. Have you looked at some of the free apps available from the Google Play Store?, My wife uses the FillUp app on her phone to track her Yaris. If you're only tracking the gas expense it does it very well and calculates a lot more fuel consumption statistics as well as provide some graphs. I use the MyCars app for the Prius as that one also tracks maintenance and repairs. It provides graphs, pie and bar charts as well as breaking down many of the stats by month, quarterly and annually. It allows you to customize some things as well as export your info as a .csv file for backup.

    I do have a question about your filling routine. With the warnings about not topping off the tank and stories of expensive repairs, aren't you worried that extra click at the pump might eventually take its toll on the charcoal canister in the vapor recovery system?
     
  5. Merlock

    Merlock New Member

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    Thanks I'll try the apps.

    I've never heard of problems from an extra click, but I've never looked into how that system works. I'd imagine there's some tolerance there for this kind of thing. I do the extra click to remove the chance of those random clicks that sometimes happen well before the tank is full. So I figured an extra click would reduce error.

    I'm not sure to be honest, I'll have to look into it more.
     
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  6. Mendel Leisk

    Mendel Leisk Sand Pounder

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    I'm doing similar: note current odo reading, subtract odo reading from last fill up odo reading, use that with gas pumped. Basic biz, and many ways you can crunch the numbers: paper and pencil, calculator, spreadsheet.
     
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  7. dolj

    dolj Senior Member

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    It looks good to me, but I just have a few questions about the first entry on 17/01.

    1) How did you arrive at the miles of 544.4 on 17/01?
    2) You said your sheet shows the ODO at fill up, but I don't see that.

    I'm presuming the last column is your calculated MPG (UK).

    Hope you don't mind the 2nd set of eyes.
    You could use the Fuelly site (fuelly.com) and the fuelly app. You need to enter ODO and 2 of the following 3:
    • litres
    • price/litre
    • total paid
    the third will be calculated. I enter ODO, litres and total paid leaving price/litre to be calculated.

    hope this helps
     
    #7 dolj, Jun 9, 2017
    Last edited: Jun 9, 2017
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  8. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Here's a break down of my spreadsheet method. Columns A, B, C and F are entered data:

    upload_2017-6-9_6-54-22.png

    And the formulas (at row 122):

    Column D: =C122-C121
    Column E: =B122*100/D122
    Column G: =(E122-F122)/E122*100
    Column H: =235.214583/E122

    I also tally the total liters since commencement, divided by the total kilometers. This is basically the same as my fuelly badge. It's not quite since the car was new, I started around 2000 km's:

    upload_2017-6-9_6-59-30.png

    And the formulas (at column M):

    Row 2: =SUM($B:$B)
    Row 3: =SUM($D:$D)
    Row 4: =M2*100/M3
    Row 5: =235.214583/M4
    Row 6: =AVERAGE(F:F)
    Row 7: =AVERAGE(G:G)
     
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  9. gta_

    gta_ Active Member

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    I use Fuelly.com's app to enter as I pump my gas each time. I enter ODO, Gallons, and Price as mentioned above. The app is called GasTracker+ . I can also go to fuelly.com if needed.
     
  10. andrewclaus

    andrewclaus Active Member

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    I agree, don't do that extra click. I can't see the need, and it's recommended to not do that.

    On the spreadsheet, if you ever do a lifetime average, just remember the average is not the average of the averages.

    A great boss I had told me the worst errors in the world are spreadsheet errors.
     
  11. Mendel Leisk

    Mendel Leisk Sand Pounder

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    It seems to me there's two ways to do a summary average. You can do an average of all your tank mpg's. Doing this will be close, especially if your fill ups are uniform. Or, you can add up all the gas consumed, and the total distance travelled, do the mpg calc from those values. The latter will be deadly accurate.

    Well as long as you haven't screwed up a formula, lol. Coming at it from two directions is a good tact: see if you get the same resul.
     
  12. Janice N

    Janice N Member

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    Another app: fuelly
    I see it in the signatures of a few posts. I'm a pen/paper person with a small notebook in the glove box. Also an easy place to jot down maintenance, repairs, and new tires. On long road trips I add the location of the fill-up - easy way to calculate trip mpg vs day-to-day. I like your spreadsheet! Good luck.

    Posted via the PriusChat mobile app.
     
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  13. srellim234

    srellim234 Senior Member

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    I do the exact same thing.

    I have a 12 column accounting notebook in the glove box and track it all there. I transfer things to the apps, fuelly and fueleconomy.gov later. Fueleconomy.gov is so others can see what a 2008 Prius is delivering in 2017. Fuelly has some very good custom stats. The hard copy is because I'm terrible about backing things up and I don't want to lose it all the records if the phone dies. The apps are more for fun and entertainment than anything.
     
  14. Mendel Leisk

    Mendel Leisk Sand Pounder

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    Spreadsheet and Fuelly here. Websites come and go...
     
  15. CoastRider

    CoastRider Active Member

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    I've never checked it or kept a log. Will they throw me out of the club? :) I just always refill when I get down to 1/4 tank remaining. I bought this Prius so I could RELAX and never be concerned with mpg or crunching numbers. it's been very enjoyable to drive. No worries.
    Happy Motoring :)

    (Spreadsheets? Accounting notebooks? Fueling websites? Holy Cow. I guess I'm in the "just drive it" camp. I never wanted to be an accountant or a tax man or a lawyer in a Prius. :))
     
    #15 CoastRider, Jun 10, 2017
    Last edited: Jun 10, 2017
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  16. Janice N

    Janice N Member

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    Brilliant! I just got a Prime and have been trying to figure out how to track electricity "fill-ups" as well as gasoline. More columns would certainly help. Do you track maintenance/repairs inline with gas or do you have a different section? I'm curious how detailed your book is. It sounds awesome.
     
  17. srellim234

    srellim234 Senior Member

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    I track it all chronologically.

    I use the 9"x7" 80 page, 12 column Adams hard bound book available at Office Depot. From left to right I have columns labeled
    Date, Location, Odometer, # of miles, PPG (price per gallon), Gallons, Total Price, MFD MPG, Calculated MPG, Notes
    The Notes area spans the last four columns for detailing repairs, other purchases ("car wash" , "5,000 service", "Prolong Deluxe battery conditioning package", etc.) and general notes about trips.

    Coast Rider - I do it for a multiple reasons. I enjoy just driving the car, too, but the book helps me
    1. See if anything's amiss. If I have a lot of 42+ mpgs in a row and then all of a sudden I see multiple 37s I'm looking for a reason. It may just be the car has been run on short hops around town but it also might be the car has a mechanical or electrical problem that needs to be addressed.
    2. Should I ever part with the car through trade-in or private sale I'll be able to ask for a higher price with such meticulous records. I have a file folder in the house with repair and maintenance receipts (I don't mess with gas receipts).
    3. It makes it incredibly easy to verify or refresh our memories about the places we've been and the dates we were there.
     
    #17 srellim234, Jun 10, 2017
    Last edited: Jun 10, 2017
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  18. CoastRider

    CoastRider Active Member

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    That makes good sense, thanks. One thing I've noticed about my Gen4, is the mpg display changes very little. I know it's not 100% accurate, but I'm just making the point that it is very consistent and always seems to stay between 58 and 62. I'm very happy with my Prius. I hope I am still saying that 10 years from now. :)
     
  19. srellim234

    srellim234 Senior Member

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    I'm not familiar with how the mpg display works on the Gen 4. On the Gen2 we have to manually hit a reset button on the display to reset it each tank. When we fill it the miles reset to zero but the MPG does not. Without the reset the mpg would change less and less as the tanks add up. Do you have to manually reset it in the Gen4, too?
     
  20. CoastRider

    CoastRider Active Member

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    To be honest, I rarely monitor it or keep track of MPG. But when I was, you just press and hold the trip button on the steering wheel and it resets the miles back to zero and mpg back to zero.

    And you can also go into the settings on the big screen, and reset all the history(?) back to zero. I was doing all that at the beginning when the car was new. Then I would refill the tank and drive a few miles and the mpg in the display would jump right back up to 60. My car likes 60. :) in reality it's probably only 55? But that's fine. I sure won't argue with that. This car has been great.
     
    #20 CoastRider, Jun 10, 2017
    Last edited: Jun 11, 2017
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