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Hot weather mileage decrease

Discussion in 'Gen 3 Prius Fuel Economy' started by Tom183, Jun 18, 2010.

  1. Cactuscoug

    Cactuscoug CactusCoug

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    We too have noticed a drop in mpg from 50 to 45 when driving around town (Tucson) and running errands. When in and out of the car alot, the AC is constantly having to re-cool the cabin from 140-degrees to mid-70's.

    My wife learned this week, that by turning the AC from "auto" to "two bars," the mpg shot back up near 50!
     
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  2. Rokeby

    Rokeby Member

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    In Ballamer, so far this summer has been unseasonably hot and dry
    with daily temps running in the mid to upper 90's with occasional
    excursions above 100 degF. This is what we expect in mid to late
    August... I don't even want to speculate what August is going to be like.

    This follows a winter of record breaking snowfall... we all speculate if
    there's a connection; neither global warming nor cooling, but much
    larger seasonal temp swings.

    I hate to use the airco, but this year I've relented and set it at 78 degF.

    I'm seeing FE reductions of 5 -10 MPGs despite trying numerous hyper-
    mileing tricks/tactics. The variation in MPG losses is due other driving
    condition effects; traffic, etc.Amapola is a Gen II.

    With a ScanGauge, which shows SOC in 1/2% steps, it is easy to see
    the effect of the airco. Stopped, when the ICE isn't running, SOC can
    drop 1%+ a minute. Yikes! With the OEM guaging, it's difficult to detect
    the slow, minute-by-minute HV drain, resulting in more frequent ICE-on
    to keep the HV battery in the HSD's operating preferences.

    This ain't what the song was talking about:

     
  3. Airbalancer

    Airbalancer Active Member

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    :confused:

    2 bars , do you mean fan speed?
     
  4. tickmark40

    tickmark40 New Member

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    I have been running my A/C on 75 (f) since I bought it the 1st of May. I can not see any effect on the mpg since my numbers continue to go up. Maybe that is because I am getting more used to the car? The temps in Texas are in the mid to high 90s with a lot of humidity this summer. My HSI is showing a mpg of 58mpg on this tank of gas!:D
     
  5. Cactuscoug

    Cactuscoug CactusCoug

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    Yes. Two bars of fan speed.
     
  6. cit1991

    cit1991 New Member

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    Yeah but Brownwood has about as much city traffic as...say... Goldthwaite. :)
     
  7. Cactuscoug

    Cactuscoug CactusCoug

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    An update: Here in Tucson, it was 102 degrees yesterday. Yet, our mpg is now running 54.5. . . .up from the mid-40's a couple of weeks ago. The AC is set at 74-degrees and the fan at two-bars.

    The only true variable is a fresh tank of gas.

    There was an article in the local paper last week about the State busting a hand full of local stations for blending too much ethanol into their fuel. They were running 14% instead of 10%. I wonder if an untested station, one that we used, perhaps was running even more than that! That would explain the MPG discrepancy.

    We are embarking on a 5000 - 6000 mile road trip next week (West Coast, BC and back), so it is good to see the numbers back up where we expect them.
     
  8. OldArmy94

    OldArmy94 Crazy Prius Man

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    My mileage has also decreased a mile or two since we started having 100 degree days here in central Arkansas. It's not a huge hit, but it is noticeable. I am guessing that the batteries aren't charging as efficiently.
     
  9. cycle11111

    cycle11111 New Member

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    I am in Dallas where it has been 100-106F for the last few weeks. I Just filled up yesterday and got my best mileage on an entire tank of 54.1mpg. I run the Ac at 77-79F but go down to 75/74F when my spouse is in the car (her call not mine).
     
  10. exuaflag

    exuaflag New Member

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    I am going to give the AC tip a try. Do you think the humidity has anything to do with MPG in the summer? The actual temp here is about 95, but the heat index is about 110.
     
  11. qbee42

    qbee42 My other car is a boat

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    Humidity increases the air conditioning load. The latent heat of vaporization for water is 540 cal/ml, so every ml of water that driped out of your AC required 540 calories to condense.

    Tom
     
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  12. Erikon

    Erikon Active Member

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    This spring I regularly achieved MPG's in the 60's, summer sees 55 tops! Dead of winter I was glad to get 50 MPG! Perfectly happy with those numbers!
     
  13. lunabelgium

    lunabelgium Member

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    Here my results
     

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  14. snead_c

    snead_c Jam Ma's Car

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    Keep an eye out for gas pumps that indicate alcohol blends. It seems that Virginia stations all have a blend.
     
  15. 4md

    4md Member

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    Who's the forum's archaeologist? :D :D

    Just wanted to share, last week the temperatures here were between 100 and 105F (37 - 41C) and my mpg dropped A LOT!
    My average gas mileage is around 45mpg (5.2 l/100) in the city when it's up to 86F (30C), but last week was very hot and the average mpg decreased to 34 (6.9l/100) and the car felt a lot weaker / under-powered. The ICE was running almost all the time, the SOC indicator wasn't moving almost at all (stayed at 2 or 3 bars at any time). At the first day I got scared a bit :D, but at night, when the temps dropped, everything was normal.

    offtopic: F*** climate changes, the last years winter temps here drop to -13F (-25C), and at the summer they go up to 111F (44C)...:mad:
     
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  16. bisco

    bisco cookie crumbler

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    yea, it just keeps getting whackier.