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Thread: Spring weather lets MPG climb?

  1. #1
    Senior Member Donut's Avatar
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    Spring weather lets MPG climb?

    Hello,

    I was wondering whether you had the same observation. As the temperatures went up the recent days, I got consistently better MPG values on my commute; from 41 MPG to 46.
    It would be great to know what contributes most to the better economy. I have three causes in mind: 1. better driving style, 2. temperature, 3. engine breaking-in.

    What is your experience?

    All the best


        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 47.8 mpg (US) ... 20.3 km/L ... 4.9 L/100 km ... 57.3 mpg (Imp)


  2. #2
    Outside temperature has a big impact on fuel economy!

    1) Do you idle more in cold weather to keep the car warm or warm it up?

    2) Tire pressure increases as temps go up. Higher pressure helps MPG.

    3) Rolling resistance goes down as temps go up. Even at exactly the same PSI, a warm tire rolls more easily than a cold one.

    4) Lower average engine temperature when it's cold out. In the winter, an engine takes longer to reach operating temperature and cools off faster when shut off. Since the engine management system orders up a richer mixture when cold (proportionately more fuel in the air/fuel combination), more fuel is being burned overall.

    5) Thicker lubricants when cold. Non-synth engine oil thickens as it cools. So does transmission oil and even bearing grease. More energy is needed to overcome the added drag these cold lubricants cause.

    6) Higher electrical loads in colder temps. We generally use electrical accessories more often when it's cold & dark:
    - lights (in higher lattitudes it's darker in the winter)
    - rear window defroster / front window defroster which turns on the A/C compressor
    - heater blower motor

    7) More aerodynamic drag when it's cold. Aerodynamic drag is proportional to air density, and the density increases as temperature drops. For every 10 degree F drop in temperature, aerodynamic drag increases by 2%.

    Not brushing snow off the top of the car hurts MPG too.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


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    Administrator Daox's Avatar
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    Temperature has a huge effect on mileage. Gasoline refineries also switch to a 'winter blend' gas during cold months and it also doesn't return quite as good of mileage.
    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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    On that basis we should get great mpg here in Asia. Not sure it really makes much difference.

  7. #5
    Except that you end up undoing a good portion of the efficiency gains of higher temps through constant use of the A/C.

    All the points are well documented. If you look at the fuel economy graph of anyone who goes through big seasonal temperature swings while doing the same daily commute, you can see the impact.

    EG: 4 years worth of tracking from someone who lives in the northern US (Michigan):

    Name:  graph4823.jpg
Views: 345
Size:  18.3 KB

    You can see the pattern of winter lows & summer highs. http://ecomodder.com/forum/em-fuel-l...vehicleid=4823 -- for dates to go along with the graph.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


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    Carmageddon m4v3r1ck's Avatar
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    Yeap .... it does makes a difference. Metro has put it very nicely and very much in detail

        __________________________________________

        click to view fuel log View my fuel log 2013 Mirage 1.0 manual: 47.5 mpg (US) ... 20.2 km/L ... 5.0 L/100 km ... 57.0 mpg (Imp)


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    High Speed Drifter RedDE5Spd's Avatar
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    Quote Originally Posted by MetroMPG View Post

    6) Higher electrical loads in colder temps. We generally use electrical accessories more often when it's cold & dark:
    - lights (in higher lattitudes it's darker in the winter)
    - rear window defroster / front window defroster which turns on the A/C compressor
    - heater blower motor

    Why would the a/c compressor run with the windshield defrost?
    Mine doesn't, unless I have the a/c turned on.
    -Billy


        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage DE 1.2 manual: 37.6 mpg (US) ... 16.0 km/L ... 6.2 L/100 km ... 45.2 mpg (Imp)


  10. #8
    It often runs in tandem with defrost (without illuminating the AC "on" light) to dehumidify the cabin air (helps clear the glass faster & keep it clear). It's a pretty common setup in newer cars.

        __________________________________________

        click to view fuel log View my fuel log 2014 Mirage ES 1.2 manual: 63.2 mpg (US) ... 26.9 km/L ... 3.7 L/100 km ... 75.9 mpg (Imp)


  11. #9
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    Quote Originally Posted by MetroMPG View Post
    It often runs in tandem with defrost (without illuminating the AC "on" light) to dehumidify the cabin air (helps clear the glass faster & keep it clear). It's a pretty common setup in newer cars.
    Thankfully the A/C clutch wire appears pretty easy to get to, so it's a 5-second disconnect. :P

  12. #10
    Administrator Daox's Avatar
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    Its easier to pull the fuse. You also don't have to worry about connector corrosion then.


    Custom Mirage products: Cruise control kit, Glove box light, MAF sensor housing, Rear sway bar, Upper grill block

    Current project: DIY Nitrous oxide setup for ~$100

        __________________________________________

        click to view fuel log View my fuel log 2015 Mirage DE 1.2 manual: 47.2 mpg (US) ... 20.1 km/L ... 5.0 L/100 km ... 56.7 mpg (Imp)


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