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Old 18th December 2007, 08:52   #1
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Default MYTH About Car A/C

I read an article in one of the websites which conducted a road test with the following two cases.
Case 1. Windows down and No A/C
Case 2. Windows up and A/C on
This was done to check whether the mileage is better in the case of Windows down and No A/C as most peeople were believing.
The resultant mileage was surprisingly almost same for both the cases. The argument for Windows down and No A/C is that due to the drag/wind resistance the vehicle will spend more fule to overcome when compared to a vehicle whose windows are closed & A/C on. This results in similar mileage for both the test cases.
The moral of the story is be comfortable with A/C or without A/C. The mileage will be almost similar.
DO we have any counter arguments for this study?

Arun
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Old 18th December 2007, 09:34   #2
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it depends. if it was tested at highway speeds then the mileage will be the same. it you test it in the city where drag is not an issue the mileage without ac will be better.
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Old 18th December 2007, 09:38   #3
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Yeah. You are right akshay. Now a days, the popular cities are so polluted that it forces you to always use the A/C. You wont be able to open the window at all.
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Old 19th December 2007, 02:17   #4
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Would second akshay on that. On the highway the drag caused by open windows would negate improvement of mileage over the use of ac with windows closed.
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Old 19th December 2007, 08:41   #5
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I wonder where the test was done?

a great deal more is required of an AC in this city than in a Northern European summer!
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Old 19th December 2007, 09:31   #6
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We Test the TipsThis is the test article from edmunds.com
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Old 19th December 2007, 10:01   #7
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American --- well, I guess they have the whole range of climates there!
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Old 19th December 2007, 10:34   #8
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Arun, what is your experience. Would have loved to hear that from you, apart from what the test has to say.
Quote:
Thad E Ginathom : I wonder where the test was done?
Exactly. There is no myth - the results will depend on the conditions that you do the test under. Highway + windows down: high drag, low FE. Might as well use the A/c. Tell us if you see similar results in city driving, and if you do, we can try understand why would it happen.
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Old 19th December 2007, 10:57   #9
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In normal driving that we do everyday AC will hurt FE. By the way the test which said "almost same" does not mention what was the small difference. Guess it favoured windows down. A small difference matters a lot in the long run.
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Old 19th December 2007, 11:03   #10
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I would have loved to test the two cases. But you know it is difficult to use the A/C in the morning time when I go to office which is hardly 10-15 minutes drive from my home(mysore). Only time I use A/C is during noon time when I go back to office from lunch at home. As you say the mileage will be almost similar in the case of highway driving with the two cases we discussed.
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Old 19th December 2007, 11:33   #11
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Arun, using a/c has nothing to do with temp settings. You can use the a/c with low/no cooling to do the same tests. If you want more info on how cooling levels affects load on engine etc, pls go through other threads here that discuss these points.

I would say that mileage on highway with a/c will be more than without a/c & windows down.
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Old 19th December 2007, 12:47   #12
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It would be true in the case of highway.

The drag would be there when you cruise on the highway. In city driving, especially bangalore, there would not be any drag and without A/C will give better mileage.
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Old 19th December 2007, 14:01   #13
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The ideal situation would be to roll the windows up & drive without the AC. This will give you the BEST Mileage, though you can do this only if its cold outside.
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Old 19th December 2007, 14:31   #14
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But then you will suffocate if there is no circulation of air even though small amount of air comes through fresh air vents.
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Old 19th December 2007, 14:48   #15
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True!
But I guess it depends on type of driving as well.
On highways, itís a no-brainer. While doing a 100 with your windows down your creating more wind turbulence and drag than the power youíd loose with the AC on.
Also the Aircon compressor steals less power when the engine sits at a constant RPM and that obviously doesnít happen in the city.
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