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Canadian fuel economy ratings changed, more realistic?

Discussion in 'Gen 3 Prius Fuel Economy' started by Mendel Leisk, Nov 5, 2014.

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  1. fuzzy1

    fuzzy1 Senior Member

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    By any chance, could that similarity be described as 'identity'?

    Or are there some differences larger than can be attributed to conversion and rounding?
     
    #21 fuzzy1, Nov 5, 2014
  2. GregP507

    GregP507 Senior Member

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    I make the same trip every day I go to work. I reset the trip-meter just before I depart, and after it warms up (if necessary). In July I was sometimes getting 3.7 L/100 km, but more often it was 4.2, and occasionally 4.5, so the average was probably around 4.2.

    As a rule, I wasn't warming up the car before I departed during the summer. Now that it's usually around freezing in the morning, I warm it up with the remote starter, and then reset the trip when I depart. I don't think the warm-up is relevant to mileage when it's only for interior heat, and runs longer than necessary to warm up the engine.
     
    #22 GregP507, Nov 6, 2014
  3. Mendel Leisk

    Mendel Leisk Senior Member

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    A couple of points:

    1. You're cherry picking your mileage, doing things like resetting the trip meter after the car's warmed, then reporting the after warm up number that the car tells you, for a single trip.

    2. Not sure about 2012, but my 2010 in-dash display of liters per 100 km is currently 7.5% optimistic. This is after calculating an accumulated 46000~ km's, and 2300~ liters of gas.
     
    #23 Mendel Leisk, Nov 6, 2014
  4. GregP507

    GregP507 Senior Member

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    You can call it cherry-picking, but I consistently eliminated stationary warm-up from the mileage number. If anything, it would have skewed the data.

    The only penalty might have been the "warm-up while driving" phase in the summer, but that would have counted against the mileage, if anything, but my mileage was consistently higher in the summer.
     
    #24 GregP507, Nov 6, 2014
  5. Mendel Leisk

    Mendel Leisk Senior Member

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    Yeah, there's nothing wrong with monitoring mpg for a trip. We do a run into town quite often, and my ScanGauge shows mpg (well, liters per 100 km) for that trip only. I can get a feel for the penalty for driving in the rain with heat/defog selected (activates AC, as I just discovered). And just generally, it shows what works, what doesn't.

    Still, it becomes meaningless, to report short runs, warmed up. I mean, I can gas up with fully warmed engine at Chevron, at the head of a looong drop down onto the Barnett Highway eastbound, pretty much roll downhill for kilometer, then set cruise and roll very conservatively to our place in North Coquitlam, sometimes pretty much completely ev'ing the last kilometer.

    In summer, in good weather, the trip meter will be showing crazy good numbers, but it's meaningless. Into everyone's life comes warmups, lousy weather, freezing weather, snow tires, winter gas, short trips, and so on.
     
    #25 Mendel Leisk, Nov 6, 2014
  6. Tideland Prius

    Tideland Prius Moderator of the North
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    I agree. If you don't include the warm up, then you get the 3.7L/100km that NRC previously reports It's not hard. I've gotten as low as 3.2L/100km (73.5 US mpg) once when I refuelled near the end of the day, so the car is fully warmed up and I drove in Super Highway Mode to WEM and back. You can see that the "warm up" on the return trip is around 4.8L/100km for that 5 min segment; typically it's over 10L/100km.

    SHM1.jpg
     
    #26 Tideland Prius, Nov 6, 2014
  7. Tideland Prius

    Tideland Prius Moderator of the North
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    You mean identical? It's a very good possibility that they are identical.
     
    #27 Tideland Prius, Nov 6, 2014
  8. HaroldW

    HaroldW Active Member

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    My last tank. Fill up took 40.5 lters. H
     

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    #28 HaroldW, Nov 6, 2014
  9. SageBrush

    SageBrush Senior Member

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    About that 'real world' comment.
    Are we talking 0C real world, or -40C real world ?
    Does the real world have an engine block heater ?

    Realistically, I have verified with instrumentation that my Prius (v)agon enters stage III after about 0.75 mile when the weather is in the 60sF, and I can hit 60s MPG(us) easily with a 4.8 mile round-trip. That seems so at odds with 'real world,' I'm wondering if my car is malfunctioning.
     
    #29 SageBrush, Nov 6, 2014
  10. Mendel Leisk

    Mendel Leisk Senior Member

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    Block heater is something we've got, use religiously, year 'round.
     
    #30 Mendel Leisk, Nov 7, 2014
  11. Mendel Leisk

    Mendel Leisk Senior Member

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    Here's an ad in this morning's Province paper:

    Capture.JPG

    The above's a 2015 vehicle. And here, from the Canadian fuel rating guide:

    Capture.JPG

    So they're playing by the rules. Nice to see. I have expected to see them following the old rating system. Still, there's a sad gulf between hwy and city ratings.
     
    #31 Mendel Leisk, Nov 7, 2014
  12. SageBrush

    SageBrush Senior Member

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    ^^ The ratios of CO2/km and $/year between cars (e.g the Malibu) are different. Error ?
     
    #32 SageBrush, Nov 7, 2014
  13. Mendel Leisk

    Mendel Leisk Senior Member

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    Not sure what's going on there. Assuming the last line is some base vehicle, and (obviously) corresponds to the one in the ad. The next line up has smaller engine displacement, different fuel type. Maybe turbo model? Ahh: see the "X" fuel is regular, and "Z" is premium (page 5 of the guide).
     
    #33 Mendel Leisk, Nov 7, 2014
  14. SageBrush

    SageBrush Senior Member

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    A quick calc suggests that the Co2/km is wrong in the line I checked -- The Malibu 2.5L you circled.
    What ratio of hywy/city is used ?
     
    #34 SageBrush, Nov 7, 2014
  15. Mendel Leisk

    Mendel Leisk Senior Member

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    Is there a direct correlation between fuel economy and CO2 emissions? I'm asea, no idea how they work that out. Maybe variation due to fuel type?
     
    #35 Mendel Leisk, Nov 7, 2014
  16. SageBrush

    SageBrush Senior Member

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    So long as the fuel type is the same, the correlation is around 99.8% IIRC, and higher if tailpipe emissions are similar.

    Fuel is ~ CH2. The MW of carbon is 12 and hydrogen is one.
    Ignore the Hydrogen,
    So C -> CO2, and tailpipe emissions measured in the mg/km range.
    These cars consume about 100 ml of petrol per km, which contains ~ ((12/14)*74) = 63 grams of source carbon and 63*44/12 ~ 233 grams of CO2.

    So by this straightforward chemistry, the error is considerably less than 1:200
     
    #36 SageBrush, Nov 7, 2014
    Last edited: Nov 7, 2014
  17. Mendel Leisk

    Mendel Leisk Senior Member

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    So must be the fuel type variation?
     
    #37 Mendel Leisk, Nov 7, 2014
  18. SageBrush

    SageBrush Senior Member

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    I doubt it. By fuel type I meant e.g. petrol Vs diesel, but that difference is clarified in table.

    Differences in octane value would make very little difference, if any.
     
    #38 SageBrush, Nov 7, 2014
  19. Mendel Leisk

    Mendel Leisk Senior Member

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    I calculated an average of hwy and city. Then multiplied by the factors I found on this page:

    Capture.JPG
    (Address: CO2 Emission Ratings for your Car provided by RightCar NZ)

    I've highlighted those values, in this:

    upload_2014-11-7_7-3-42.png

    By that method, my calc'd CO2 values are a bit different, but not much. And the diff is very consistant, and likely because they're not calcing with a simple average of hwy and city?
     
    #39 Mendel Leisk, Nov 7, 2014
  20. SageBrush

    SageBrush Senior Member

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    Your calculated numbers are the same as mine, so based on a 50:50 split of highway/city the CO2 consumption is ~ 15% than published. That is a lot more than a bit.

    70:30 anyone ?

    And even if this is the explanation, it does not explain the ratios discrepancy I mentioned.
     
    #40 SageBrush, Nov 7, 2014
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