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Author Topic: Highway driving and saving gas in the summer heat Back to Topics
BLTHNDR

Veteran Author
Chicago

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Message Posted: Jul 17, 2012 9:12:09 PM

Leave your air on and drive with the windows closed, much less drag on your auto and more comfortable too. Try it and compare the results.I hope its true.

[Edited by: BLTHNDR at 7/17/2012 9:12:49 PM EST]
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dgsteven
Champion Author Los Angeles

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Message Posted: Jan 3, 2013 4:10:01 AM

always keep comfort for myself
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dieharder
Sophomore Author Ottawa

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Message Posted: Nov 7, 2012 12:09:50 PM

Newer cars have more efficient AC systems than older vehicles. These days it is hard to find a vehicle that gets better gas mileage windows open than closed with AC on.
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13Octane
Champion Author Tucson

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Message Posted: Nov 5, 2012 5:27:20 PM

agree
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sagnat
Champion Author Riverside

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Message Posted: Oct 8, 2012 3:09:22 AM

If the temp is below 80 I'll crack all the windows about 1-1.5 inches. Once it hits 80 I put on the A/C. On long drives I will leave the recerc on and shut the A/C off when climbing hills and turn it back on going down.
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charladan
Champion Author Virginia

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Message Posted: Oct 8, 2012 1:17:56 AM

yes
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buickentury
All-Star Author Madison

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Message Posted: Jul 21, 2012 10:51:47 PM

Windows down provided its not extremely hot. AC really seems to sap the power (and mileage) on my vehicle.
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Titanic1985
Champion Author South Carolina

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Message Posted: Jul 21, 2012 3:18:31 AM

Hello DHomz. You said, "Also, you can turn the temperature up so the AC doesn't run all the time, it doesn't have to be on the coldest setting. The A/C clutch will cycle less often." This is not a true statement. The temperature setting ACtually is allowing more heated water from the engine cooling system to mix with the colder air-conditioned air. Auto air conditioning is very simplistic. First, the A/C must be turned on. It's main controls are computer or vACuum, which can turn off the A/C clutch when more engine power is required or the temperature of the engine increases beyond what a cooling system can handle. The evaporator coil in the dash has a temperature probe to prevent icing up of the coil which if allowed to freeze would block air flow from the interior fan or burst the coil itself and the A/C off switch which terminates DC power to the A/C compressor clutch. Technically, the A/C clutch is not thermostatically controlled unless you have climate control. Turning down the fan speed will cause the evaporator coil to sense less air flow, the coil will get colder faster and the AC clutch will disengage sooner & more frequently. You will experience diminished cooling in the vehicle's cabin. All of these switches & sensors are in series to control the compressor clutch. If one of these opens, the A/C clutch disengages.

Corn440 has it right when he says, "I think the key is max/recirculated A/C instead of cooling and dehumidifying the great outdoors." To ease the load on an AC unit, it is best to first set your fan on high to exhaust the high interior temperature. Most vehicles have exhaust vents in the rear, usually behind the tail lights. Then put the A/C in the recirculate mode which is predominately interior air with a small mixture of outside air to prevent stale interior air. Recirculated air is not 100% interior air.

Simply put auto A/C works when the compressor runs. Controlling the A/C compressor clutch regulates just how cold the temperature is, assuming you have sufficient Freon and a properly working system.

Further information regarding auto A/C can be found by using Google searches as there isn't enough spACe on this forum to go into every detail.



[Edited by: Titanic1985 at 7/21/2012 3:25:03 AM EST]
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KansasGunman
Champion Author Kansas

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Message Posted: Jul 21, 2012 12:43:36 AM

The only times my window comes down is to spit or shoot.
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dagherrera
Sophomore Author Indianapolis

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Message Posted: Jul 20, 2012 10:35:08 PM

Air conditioning when over 85-90 windows up on freeway.
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DHomz
All-Star Author Ontario

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Message Posted: Jul 20, 2012 10:45:54 AM

If you use your A/C and drive the speed limit or slightly over (65-70mph or 110km/h), it's far more efficient than driving with windows down and doing 75-80mph or 120km/h. Also, you can turn the temperature up so the AC doesn't run all the time, it doesn't have to be on the coldest setting. The A/C clutch will cycle less often.
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Jkent1953
Champion Author Salt Lake City

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Message Posted: Jul 20, 2012 10:37:15 AM

Comfort is king.
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Houckster
Champion Author Atlanta

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Message Posted: Jul 20, 2012 8:43:58 AM

BLUEBERRYFOCUS: it would be interesting for you to provide a link for this. All the articles I've seen state the opposite.
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BlueberryFocus
All-Star Author Rochester

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Message Posted: Jul 19, 2012 10:20:52 PM

I read an article recently that driving with the windows down, even on the highway is significantly more efficient than using the A/C. The test vehicle was a honda accord I believe.

Mythbusters also confirmed this when they drove two identical SUVs at 55 mph with cruise control around an oval track with 5 gallons of gas in the thanks - the SUV with the windows down and A/C off drove about 15% further before running out of fuel.
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BLTHNDR
Veteran Author Chicago

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Message Posted: Jul 19, 2012 9:46:06 PM

Thats what I'm talken about Mr corn!
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Corn440
Sophomore Author Illinois

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Message Posted: Jul 19, 2012 7:49:46 PM

Running MAX A/C during a 2,000 mile road trip in 100-degree heat had degligible effect on gas mileage. '02 Durango 4WD 4.7L Auto got 17.2 versus EPA's 16 estimated. Needless to say I was OCD about babying the throttle the whole trip.

I think the key is max/recirculated A/C instead of cooling and dehumidifying the great outdoors.
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cheapmonkee
Champion Author Portland

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Message Posted: Jul 19, 2012 4:29:32 PM

I only use it for short term periods usually only a couple minutes or less. Such as coasting down hills or as coming to a stop. Or longer when sissy passengers start crying.
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PhilT08
Champion Author Buffalo

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Message Posted: Jul 19, 2012 2:56:08 PM

Houckster, The point I was making is that people are often penny wise but dollar foolish.

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Houckster
Champion Author Atlanta

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Message Posted: Jul 19, 2012 9:59:36 AM

REB4 writes: And if wife's in car, it's on when she says so...
_____
Very wise REB4, you gotta sleep some time.
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rjro
Champion Author Albany

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Message Posted: Jul 19, 2012 8:24:43 AM

Depending on temp and humidity is how I determine if I use air.
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Houckster
Champion Author Atlanta

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Message Posted: Jul 19, 2012 8:11:18 AM

Relative to PHILT08's comment: What's the point here? It seems to me he's trying to portray people who like to conserve fuel as somewhat silly. Save a drop of gas here but be energy wastrels elsewhere?

I don't use the air much or at all around town even when the temperature is over 90. I just like saving that gas and avoiding the pollution that is caused. It's just a personal preference and even if it is hot outside there's enough of a breeze from driving to keep me sufficiently cool. I've always liked to keep fuel consumption low, even when gas was 32ยข for regular.

At home I will use the A/C but I try to keep it at a high level to minimize power consumption and I bought the highest efficiency unit I could find. I use fluorescent lights and only the minimum lighting necessary.

There is a great deal of satisfaction in conservation.

[Edited by: Houckster at 7/19/2012 8:13:50 AM EST]
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W707
Champion Author Pennsylvania

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Message Posted: Jul 19, 2012 2:21:10 AM

I''ll take the ac anyday
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PhilT08
Champion Author Buffalo

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Message Posted: Jul 18, 2012 10:48:37 PM

topics like this make me wonder about those who won't use A/C in their car because they might lose a fraction of a MPG. do these same people sit at home sweating because they are too cheap to spend a few bucks on electric for A/C at home ? do they turn off all lights and use candles at night ?

I bet these same people dont think twice about burning considerably more gas at the drive through.
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WEPSMAN
Champion Author South Dakota

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Message Posted: Jul 18, 2012 10:11:25 PM

I will take the cost for comfort.
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PatAZ
Champion Author Tucson

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Message Posted: Jul 18, 2012 5:09:59 PM

I feel sorry for people who don't or can't use their air conditioning around here.

[Edited by: PatAZ at 7/18/2012 5:10:56 PM EST]
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Titanic1985
Champion Author South Carolina

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Message Posted: Jul 18, 2012 1:32:43 PM

Auto air-conditioning is an expensive option, even if its price is buried within the cost of the vehicle. It really does not make sense not to use it, if you have it in your vehicle and it is working properly. Other reasons for using it can be health related (e.g. intense heat & high humidity) or just to keep the system functioning properly. I have just handled several A/C issues off line on the Car Talk forum. You must use the A/C whether it be R12 or R134a to circulate the oil within the system and activate the belt driven clutch.

Houckster made a valid comment when he said, "In the years to come, more and more cars will come with electric air making the choice to use air easier." The advent of the beltless air compressor is soon to be a reality as auto manufacurers continue to increase MPGs. This type of system has been used in conversion vans for years to provide A/C & heat to the rear unit. The only issue there is an extremely large battery (weight) and alternator (expense + weight).

Reb4 probably gave the best reason of all when he said, "And if wife's in car, it's on when she says so..." Forget saving gas when the comfort of your passengers should be your major concern.
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MsPeachi747
Veteran Author Cleveland

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Message Posted: Jul 18, 2012 10:39:59 AM

If you have rain guards on your front and rear windows, would opening the window not beyond the rain guards on the highway actually cut down on the aerodynamic drag placed upon your vehicle?
This information is not included in the article. I do this on hot sultry days traveling from Cleveland to Akron.
Anybody with any further information, please show me the facts!
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reb4
Champion Author Chicago

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Message Posted: Jul 18, 2012 9:28:42 AM

if it's 100 there is no way I'm not using a/c...

in fact, it goes on when temp is over 85 on highway...

And if wife's in car, it's on when she says so...
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Houckster
Champion Author Atlanta

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Message Posted: Jul 18, 2012 9:25:10 AM

MERTIEMAN writes: Just how long did it take you to figure out this brilliant solution?
_____

C'mon, a lot of people don't have your amount of experience so the comment might be helpful to a lot of people. If people just posted topics helpful to you we wouldn't have any.
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Houckster
Champion Author Atlanta

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Message Posted: Jul 18, 2012 9:09:38 AM

Here's an article that some may find interesting: A/C and fuel economy

Among the findings: 1) 40 MPH is about the speed when it's better to use the air; 2) the more aerodynamic the vehicle, the more fuel efficiency is lost; 3) the wind resistance a vehicle encounters at 70 MPH is 4X that at 35 MPH.

In the years to come, more and more cars will come with electric air making the choice to use air easier.


[Edited by: Houckster at 7/18/2012 9:16:40 AM EST]
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MertieMan
Champion Author Lexington

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Message Posted: Jul 18, 2012 9:04:30 AM

Just how long did it take you to figure out this brilliant solution?
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bithehr
Champion Author Atlanta

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Message Posted: Jul 18, 2012 8:34:27 AM

good to know
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Dennis783
Champion Author Des Moines

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Message Posted: Jul 18, 2012 7:43:14 AM

I agree with the OilerFan
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OilerFan
Champion Author Tulsa

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Message Posted: Jul 18, 2012 7:40:56 AM

In 100 degree weather, I'm running the airconditioner whether it saves gasoline or not.
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