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Author Topic: The end all verdict to A/C vs. windows down! Back to Topics
PD
Moderator
Message Posted: Jul 22, 2011 12:41:20 PM

There have long been battles between people investigating A/C vs. use of windows, so let's face it, will we ever find a true solution that always holds true? Perhaps not, but we may get close.

For the ultimate verdict I was going to compare several credible sources and ultimately see if there was any sort of rhyme or reason to their research and testing, if they did any.

First up? HowStuffWorks.com. While definitely not a leading researcher, they've looked at published reports from credible sources and seemingly have a good fix on this battle.

Taken directly from HowStuffWorks.com,

"Based on a study conducted by the Society of Automotive Engineers (SAE), driving with the windows up and the air conditioning...

Visit GasBuddy Blog for full article
REPLIES (newest first) Post a Reply
Sydman
All-Star Author Grand Rapids

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Message Posted: May 27, 2014 6:31:26 PM

I like fresh air from the windows at lower speeds unless it's very humid. High humidity demands AC at any speed (regardless of gas use).

[Edited by: Sydman at 5/27/2014 6:32:27 PM EST]
E-Squirrel
Champion Author Orange County

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Message Posted: May 26, 2014 8:32:11 PM

I have never tried to duplicate the test conducted here, with larger engine vehicles. I do however have 100,000s of miles driving experience with smaller engined vehicles, with engine sizes down to 1500 cc. I can tell you without question, that in these vehicles, operation of the air conditioner will lead to a loss in mileage of 3-5 miles per gallon. Opening one or two windows partially will not result in more than 1-2 miles per gallon loss of mileage at highway speeds.

Since I routinely drive vehicles with small engines, I have no uncertainty about how to maximize their economy, but its good to know in case I ever have to rent one of these larger vehicles.
PatrickHenry
Champion Author Illinois

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Message Posted: May 25, 2014 8:18:33 PM

I think too many variables were ignored: window(s) partially open, specific vehicle aerodynamics, sporadic A/C use, wind direction and speed, etc.
Cityscape
Sophomore Author British Columbia

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Message Posted: May 25, 2014 3:21:21 AM

I don't have A/C.... But I have a moonroof with aerovents! :)
Raider44
Champion Author Allentown

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Message Posted: May 25, 2014 12:04:02 AM

good to know.
Wanda127
Champion Author Florida

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Message Posted: May 24, 2014 9:58:40 PM

Thanks for the info
Pimousse
Champion Author Detroit

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Message Posted: May 24, 2014 11:34:54 AM

I don't have a/c so my windows are always down.
xkegroller
Champion Author Knoxville

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Message Posted: May 24, 2014 8:37:21 AM

didn't they prove this on Mythbusters a few years ago!
Rick52
Champion Author Milwaukee

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Message Posted: May 24, 2014 7:07:59 AM

Gas Prices are to High..
JayTheGasHunter
Sophomore Author Indianapolis

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Message Posted: Aug 5, 2011 8:22:30 AM

Very good to know and good sources. Thank you!

-J
SavingInNC
Champion Author North Carolina

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Message Posted: Aug 3, 2011 5:19:48 PM

Got to use the ac
z3dude
Champion Author Massachusetts

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Message Posted: Aug 2, 2011 7:57:55 AM

Now is the time to raise the federal fuel excise tax!

The federal gasoline tax raised $25 billion on gasoline in 2006. The tax was last raised in 1993, and is not indexed to inflation. The federal gas tax has experienced a cumulative loss in purchasing power of 33 percent since 1993. An increase of 10ยข/gal would bring approximately $20 billion of annual revenue into the Highway Trust Fund.

WilW
Champion Author Atlanta

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Message Posted: Jul 29, 2011 2:11:00 PM

traindude wrote: "less stuff moving, engine works less.....end of story".

Das jus ignunt.
ccf_jeff
Champion Author St. Louis

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Message Posted: Jul 28, 2011 2:23:03 PM

I remember someone telling me of riding with a friend in an old VW Bug. They were air cooled in those days and didn't come from the factory with air conditioning, or at least I believe this one had an aftermarket airco unit.

The owner was a very big guy and my friend said that when he turned the air conditioner on he could feel the car noticeably slow down as it struggled up a small hill.

I imagine the newer cars with the more powerful engines have a less marked difference in performance and gas mileage when kicking on the airconditioner.
baddog58
Champion Author Texas

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Message Posted: Jul 27, 2011 3:11:25 PM

I'm old enough to remember when turning the A/C on made a noticeable difference in engine performance; not so much today.
traindude
Champion Author Virginia Beach

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Message Posted: Jul 27, 2011 9:05:17 AM

less stuff moving, engine works less.....end of story
regulate_now
Champion Author Indiana

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Message Posted: Jul 26, 2011 1:39:35 PM

The choice is made at the time of purchase- not when you decide to put the windows up or down... A vehicle without a/c installed gets better gas mileage than an identical vehicle with a/c installed (whether you use it or not).
badboy72714
All-Star Author Arkansas

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Message Posted: Jul 25, 2011 9:42:11 PM

There is not enough difference for me not to use my air.
pfitzger
Champion Author Twin Cities

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Message Posted: Jul 25, 2011 4:54:31 PM

Most Peoples Skin temp is around 85 degrees F. So the temp outside matters as well as its moisture content or humidity. Over 85 outside air means moving air typically makes you hotter. The A/C inside a car dehumidifies the air if its working properly too. That makes your skin sweat more effective at cooling in the lower humidity air. The human hand is a good radiator and puting it into a cold airstream or vent will chill the blood. All scenarios have practical limits and putting your hand outside the window here in Minnesota's winter could have adverse consequences.
There is NO "ULTIMATE ANSWER" . Use your head.
LEGION57
Champion Author South Carolina

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Message Posted: Jul 25, 2011 3:28:14 PM

We used to call it 4-60 AC. 4 windows down at 60 mph!
LEGION57
Champion Author South Carolina

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Message Posted: Jul 25, 2011 3:10:03 PM

Windows UP all the time- AC on when it is hot. Keep the noise and pollution out. Clean air and my Conservative Radio station on. Wonderful combination.
Eric2448
Champion Author Pennsylvania

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Message Posted: Jul 25, 2011 2:52:03 PM

ya
WilW
Champion Author Atlanta

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Message Posted: Jul 25, 2011 1:31:41 PM

txkrb wrote: "I have noticed in my daughters Nissan Sentra, I monitor the tachometer (driving a steady speed) with A/C on and with A/C off I could not see a noticeable difference in engine speed."

I don't think you have a clear understanding of the issue. It's related to drag and load, not engine speed.
txkrb
Champion Author Texas

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Message Posted: Jul 25, 2011 1:11:39 PM

I have noticed in my daughters Nissan Sentra, I monitor the tachometer (driving a steady speed) with A/C on and with A/C off I could not see a noticeable difference in engine speed
Amplion
Champion Author Oregon

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Message Posted: Jul 24, 2011 11:34:33 PM


Rolling windows down is to share your music with those around you !!!!!!
THUMP-THUMP-THUMP!!!!

BETTER TO HAVE AC !!!!!!!!!!!!!!!
remay
Champion Author Houston

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Message Posted: Jul 24, 2011 9:00:37 PM

Makes sense.
Amtrgas
Champion Author Oakland

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Message Posted: Jul 24, 2011 8:28:05 PM

Windows down at low speeds (city streets,country roads). Windows up and A/C on at higher speeds.
teafortwo
Champion Author Washington

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Message Posted: Jul 24, 2011 3:32:49 PM


Why didn't they factor in allergies and respiratory distress aggravated by road pollution?
lefthandofgod
Rookie Author San Jose

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Message Posted: Jul 24, 2011 2:42:48 PM

The difference in gas milage is very slight no matter the size of the engine... the bigger the engine the bigger the vehicle so a small car with a small engine has a small ac compressor... A diesel vehicle will show almost no milage difference do to the high torque that it has.
WalkingWV
Champion Author West Virginia

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Message Posted: Jul 24, 2011 1:12:03 PM

So the more aerodynamic your vehicle, the more it's affected by having the windows down.

My in-laws drove through the desert with the windows down to save a few dollars on gas. I'm sure that was an enjoyable ride.
fuel2use
Champion Author Seattle

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Message Posted: Jul 24, 2011 9:59:39 AM

Your mileage may vary.
DESandman99
Rookie Author New Jersey

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Message Posted: Jul 24, 2011 9:54:11 AM

Story did answer the question for many as it only does the tests with V-8 engines - larger engines to which the additional load of A/C would be relatively small. Certainly the results would be different if the tests were done on vehicles with 4 and 6 cylinder engines as the additional A/C load causes the engines in those cars to run significantly harder, and thus consume much more fuel.
Pete12
Champion Author Albany

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Message Posted: Jul 23, 2011 7:56:54 PM

Why would anybody let a slight difference in gas mileage one way or the other keep them from being cool on a hot day?
MilestoneMotors
Champion Author Allentown

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Message Posted: Jul 23, 2011 1:20:45 PM

It's really negligible on most vehicles.
Ghosty1
Champion Author Quebec

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Message Posted: Jul 23, 2011 10:51:10 AM

Hot and humid means my Air is on, cool and comfortable, windows are down. MPG is not a factor in my comfort.
leraar2
Champion Author Massachusetts

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Message Posted: Jul 23, 2011 9:14:17 AM

along another thread,
just tested drafting on a truck:
effective when within 15 feet of truck;
the taller the truck, the further you can stay back.
yesterday (102 ambient temperature in shade--probably much higher near the highway surface) had to turn off AC and turn on heat flow (low) to car heater, in order to keep engine temp within limits.
that's another indication you are really drafting:
less air is being forced through the car radiator.
was able to come off the gas pedal by almost half inch.
OTISFL
Champion Author Pensacola

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Message Posted: Jul 23, 2011 8:51:05 AM

How much did that stupid survey cost? Just plain common sense.
Rick52
Champion Author Milwaukee

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Message Posted: Jul 23, 2011 6:39:50 AM

AMEN ! ! !
RNCII
Champion Author Michigan

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Message Posted: Jul 23, 2011 3:42:05 AM

Not sure I buy it yet.
I noticed I about 3 MPG more widows down on a 35 mile street and highway drive to work than with the a/c in my truck.
WilW
Champion Author Atlanta

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Message Posted: Jul 23, 2011 2:12:31 AM

It figures. Keeping the tailgate UP on my pickup makes it more fuel efficient at highway speeds.
N5EXY
Champion Author Austin

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Message Posted: Jul 23, 2011 1:04:06 AM

No surprise here. Wind drag was known before we had AC.
CrackedLCD
Champion Author Alabama

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Message Posted: Jul 23, 2011 12:58:14 AM

Same here. Mythbusters did it a long time ago.
jjfisher
All-Star Author Toledo

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Message Posted: Jul 23, 2011 12:13:45 AM

I've been doing what Mythbusters results were for years. Up on the highway & down in the city.
WalRus49
Champion Author Boston

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Message Posted: Jul 23, 2011 12:11:35 AM

Seriously?
14Ghosty1
All-Star Author Montreal

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Message Posted: Jul 23, 2011 12:09:46 AM

Unless its really hot and humid, I prefer to drive with the windows down arouind the city.
estroh
Champion Author Indiana

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Message Posted: Jul 23, 2011 12:03:53 AM

As someone has already said.. The Mythbusters have more than covered this topic. Windows down is the way to save. Tailgate up on a pickup is the way to save.
rxman1
Champion Author Toledo

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Message Posted: Jul 23, 2011 12:03:47 AM

Just do whatever you want. For me, the windows up and the AC on. My mpg's prove it.
ACTown
Champion Author Oregon

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Message Posted: Jul 23, 2011 12:03:42 AM

It is noisier and hard on the hearing when the window is down. We had a sun roof one time and we never used it since it was so load with road noise.
NO_SWEAT
Champion Author Toronto

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Message Posted: Jul 23, 2011 12:03:37 AM

At highway speeds I will keep my windows shut and the AC on.
judgemobile
Champion Author Ohio

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Message Posted: Jul 23, 2011 12:02:12 AM

wind does NOT dehumidify,and A/C does, so A/C wins. Would you drive your car in this HEAT WAVE without A/C, just windows down ? Try it--you WON'T like it.
tampacrvdriver
Champion Author Tampa

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Message Posted: Jul 23, 2011 12:01:46 AM

I look upon this dubiously.
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