Effect of Wind on Fuel Economy

Discussion in 'Gen 3 Prius Fuel Economy' started by kutztown46, Mar 19, 2015.

  1. kutztown46

    kutztown46 Junior Member

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    A few nights ago, on a very windy evening here in eastern Pennsylvania, we took our 2015 Prius Four for a 38-mile trip. I got over 59 mpg for this trip. I realize the true number is probably closer to 55, but this was still my highest mpg trip since we bought the car a month ago. An hour later we drove home, and I got only 52 mpg. I drove both ways with the same care. There are hills going both ways but the starting and ending elevations are about the same. The only thing I can attribute the difference to is the wind. There was a stiff wind coming out of the northwest. The first trip was in a southeasterly direction, so the wind would have been at our back. During the trip home, we would have been driving into the wind most of the time.

    Does this make sense?
     
  2. Tony D

    Tony D Active Member

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    Ive noticed the same on a regular 50 mile trip that I make. I too have put it to wind. If I get in behind a large truck on the "windier" trip, the mpg will be better
     
  3. The Electric Me

    The Electric Me Go Speed Go!

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    Does this make sense?

    Sure.
    Why not?
     
  4. Easy Rider 2

    Easy Rider 2 Senior Member

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    The largest single factor in fuel efficiency is the aerodynamic drag from the air; both the result of the car's speed and the speed of the wind.

    Any wind speed over about 10 MPH can have a measurable impact.
     
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  5. bwilson4web

    bwilson4web BMW i3 and Model 3

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    Yes as these are the aerodynamic effects:
    • drag force - increases by the square of the velocity (i.e., what torque is required)
    • drag power - increases by the cube of the velocity (i.e., fuel consumption)
    • linear with air density - temperature being the primary driver, cold air is much denser, harder to push through
      • although a colder inlet air allows a little more engine power, our Prius has a heated manifold and the Atkinson cycle, double-passes the air through the cylinders also increasing temperature
    Bob Wilson

    ps. I don't know why but the title wording reminds me of a scene in the movie, Blazing Saddles. An old man, "Effect of Wind" breaks me up.
     
  6. minnyprius

    minnyprius Member

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    My smart is not aerodynamic at all. a tailwind can increase my MPG by 25%, and a headwind can reduce it by 25%. And a stiff crosswind can make lane holding a slalom event. :) During a recent road trip, I saw lots of Prii/Priuses and couldn't WAIT to get my hands on one... Oh, Gen IV, please hurry...
     
  7. walter Lee

    walter Lee Hypermiling Padawan

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    On a flat smooth dry road surface, on a clear and windless day at 70 degrees Fahrenheit, driving a fully warmed up Prius

    At speeds under 40 mph - more than 50% of the energy used to push a Prius forward is fighting rolling resistance
    At speeds over 50 mph - more than 50% of the energy used to push a Prius forward is fighting aerodynamic drag.
    At about 45 mph - about 50% of the energy used to push a Prius forward is fighting rolling resistance and
    the other 50% of the energy used to push a Prius forward is fighting aerodynamic drag.
     
  8. CR94

    CR94 Senior Member

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    "Push"? Front-drive cars pull themselves forward, and push themselves rearward.
     
  9. cyclopathic

    cyclopathic Senior Member

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    Don't discard the temperatures
     
  10. fuzzy1

    fuzzy1 Senior Member

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    If the difference was only 7 mpg, then the wind wasn't all that stiff. I've seen greater differences on other cars with much lower mpg ratings.
     
  11. GrumpyCabbie

    GrumpyCabbie Senior Member

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    Wet roads also make a surprising increase in fuel use. Wet and windy days are a perfect storm :)
     
  12. lester williams

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    On our recent trip from Ms to Az, we averaged 46.8 mpg on the way west. We mostly had cross winds there but had a tail wind home-- 50.7 mpg on the trip home. The 3,000 mile average was 48 mpg--- not bad at speeds we were running [ Texas speed limit ] So , yes, winds did factor in on our mileage. And, as Bob said above, rainy roads will hit your mpg also. As well as temps, my mpg is now above 50 since spring has sprung.
     
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