Wow - ambient external temperature REALLY matters for MPG

Discussion in 'Gen 4 Prius Fuel Economy' started by galownia, Apr 18, 2016.

  1. galownia

    galownia Previous master neon mechanic

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    Step change, almost overnight, last week from ~40s F to ~70s F. MPG up from average of about 59 to 69. 10mpg, consistently, and still climbing as temperatures rise. For instance, today's ride into work and some errands was ~37 miles and I am showing 73mpg. Temp was about 5 degress wamer this morning than it has been.

    Why: I notice in the warm temperature, the car uses EV much more. Further, the car will go in EV all the way down to 1 bar in the battery. It will also hold EV sometimes mid way between the "eco" line and the "power" line on the hybrid system display.
     
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  2. Mendel Leisk

    Mendel Leisk 'Orrible Oracle

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    Yeah, probably some temperature threshold, shifts the car to a different warm up pattern. Where you've set cabin temperature will likely have an effect too: make the difference between engine running vs shutting down at lights, when it's partially warmed.
     
  3. bisco

    bisco cookie crumbler

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    absolutely. 40 - 70 is a big change, and the corresponding mpg's make sense. the temp doesn't usually change that fast, so it's less obvious.
     
  4. pakitt

    pakitt Senior Member

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    I get similar changes in fuel consumption with my Gen3 (relatively, of course... ;) ). When the temp hits more than 10C/50F, the fuel consumption drops - not just the warm-up time and pattern changes, also there are more chances for the electric motor to do its job. Car heating has a huge impact too.

    Here is what I got today commuting back to work, with even 2 warm up cycles (I stopped at a gas station to fuel up soon after leaving work) at 10C/50F, with A/C at 19C/66F and summer tires (Michelin Primacy 215/45R17):
    IMG_8316.jpg
    That is, 11,25mi / 60mpg (with 6,2% MFD error, that is actually 56,7MPG) at 28mph average (a few traffic lights and a good stretch at constant 65km/h - 40mph speed).
     
    #4 pakitt, Apr 18, 2016
    Last edited: Apr 18, 2016
  5. JBarleycorn

    JBarleycorn Junior Member

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    Yes I notice this every spring. We have our first warm days and then my mpg goes up. Seasonal MPG changes are shown in the picture attached.

    Also there is a very noticeable mpg reduction from running the air conditioner, about 5-10%. If you work that out it means the A/C consumes about 0.001 gallons/mile, at least in my climate.

    Prius2012mpg.PNG
     
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  6. krousdb

    krousdb NX-74205

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    I find that the mid 50's F is the tipping point. You also may be finished breaking in the tires and mechanicals. Climate control is also a contributor. In colder weather, I wear a coat and gloves. I never use heat and use AC only above 80F. Cracking the drivers front and passenger rear window a few inches each helps keep the interior temps from getting too unbearable in the warmer months..
     
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  7. Trollbait

    Trollbait It's a D&D thing

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    This is true of all cars.
    It is just more noticable when the MPG value is high to begin with.
     
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  8. alfon

    alfon Senior Member

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    Our 2010 Prius mpg increases at least 10-15 % when going from mid 40-s to mid 60's in temp. Last fillup was 55.6 mpg calculated for over a 500 mile tank warmer weather. Winter would have been 47-49 mpg calculated....
     
  9. dstahre

    dstahre Member

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    I seem to remember from high school chemistry that the speed of a chemical reaction roughly doubles for every 10 degrees Centigrade rise in temperature (18 degrees F). I would expect some change in battery performance in response to ambient temperature (though I'm sure that the heat generated by using the battery helps to mitigate this somewhat).
     
  10. ucla107

    ucla107 Member

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    While higher temps yield better battery mpg, it kinda gets offset where I live... Got up to high 80s this week in LA and with my 1+ hour drive each way to/from work, I've had to use the AC so I don't melt... That dropped my mpg down, and didn't help that I was in a hurry the last couple of days and had to go 80/85mph to work and that and using the AC significantly put a dent in my mpg :(


    iPhone ?
     
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  11. dstahre

    dstahre Member

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    I hear ya on the AC. Our second vehicle is a black Jeep Grand Cherokee. With color and all the glass the AC runs constantly in the summer!
     
  12. 70AARCUDA

    70AARCUDA Active Member

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    Has anyone actually 'plotted' their MPG-numbers versus mean-daily temperatures so as to SEE what affect temperatures have on their MPG-numbers?
     
  13. bowerda47

    bowerda47 Member

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    For all you colder climate people out there. I learned a neat cold weather trick when I had my 2009 and it worked on my 2012 Prius also. If anybody interested. I will give a detailed explanation. Do not know if it would work on the 2016 Prius.
     
  14. Coast Cruiser

    Coast Cruiser Senior Member

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    I run my AC almost every time I drive, even when it's cool outside. I don't like to open the windows because of all the dirt and dust in the air. It's so dry here. Also, I hope the cool cabin temp will keep the hybrid battery cooler? Anyway, I still average a steady 60 mpg.
    Do you really drive 85 mph? I didn't think a Prius would go that fast! :eek:

    image.jpg
     
  15. FlyBoy5

    FlyBoy5 New Member

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  16. pakitt

    pakitt Senior Member

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    85mph is just 137km/h, which is a regular speed on most EU highways (limit is 130km/h in most places).
    The Prius can go up to 111mph/180kmh, and in Germany where I live, I have driven it as fast many times without any issues, even for longer stretches (e.g. 20-30 mins non stop).
    Driving a Prius at 85mph is no big deal really as it holds the road really well.
     
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  17. tzx4

    tzx4 Active Member

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    I am all ears.
    Why have you not tried this method on your 2016?
     
  18. tzx4

    tzx4 Active Member

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    I found 160 kmh to be quite comfortable and just about right, However being as I was visiting, of course I drove my turbodiesel Golf mietwagen as fast as possible. It could achieve 215kmh. Fuel economy freak that I am, I kept track of distance and fuel use. For all the continuous full throttle use and high speeds (impossible here in the USA), I was amazed to get around 6.3l/100km, that would be 37mpg. I'd love to drive my 2016 Prius on the Autobahn.
     
    #18 tzx4, May 6, 2016
    Last edited: May 7, 2016
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  19. Coast Cruiser

    Coast Cruiser Senior Member

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    I've never been to Europe. Why is there no speed limit on the Autobahn? It fries my nerves to just drive 75 on California freeways. People are crazy! I can't even comprehend reaching speeds of 100 mph or more, especially in a Prius? :eek: (Maybe on a closed, professional race track I could do it... If I was 25 again!!)
     
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  20. tzx4

    tzx4 Active Member

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    Drivers there are used to it, passing on the right is illegal, and they are very good at keeping right except to pass. One can move to the right with relative ease, but moving to the left lanes needs to be done with lots of caution. Just because one is going 110mph does not rule out some exotic car closing in from behind at another 90 mph faster! I absolutely loved it. Such fun, and such freedom!
    BTW, my fastest stretch there was a few miles at 130mph, and that was in traffic (light traffic).
     
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