A/C vs open windows

malherbe · #1 08-16-2008, 01:04 PM

At what speed does it pay to turn the a/c on? My experience is cracked windows use less fuel.

azraelswrd · #2 08-16-2008, 01:50 PM

As mentioned in that other post, based on my own experiments for my own car 45mph seems to be limit for windows open but I can push it to 50mph with cracked windows, depending on wind direction and wind noise. Too loud = close the windows

I remember from Mythbusters #38 their cutoff point for window open/excess drag was also 45mph.

lamebums · #3 08-16-2008, 03:31 PM

From my experience no matter what the speed is, the windows are better down than having the A/C on. At all times.

Depends on how old your car is and the size of the engine, though. The larger the engine, the smaller load relatively on the engine. Also, today's compressors are much more efficient than even ten years ago, and more so than twenty years ago.

I haven't used my A/C since the end of May when I had to drive 600 miles in 100 degree heat, and only after 350 miles of having my left arm sunburned to hell did I concede and crank the air. My left arm is still darker than my right arm today.

2way · #4 08-20-2008, 08:36 AM

Quote:

Originally Posted by lamebums

Depends on how old your car is and the size of the engine, though. The larger the engine, the smaller load relatively on the engine. Also, today's compressors are much more efficient than even ten years ago, and more so than twenty years ago.

I don't know about the compressor improvements. But, I agree w/lamebums. I take a much bigger A/C FE hit on the 4cyl. vs. the 6cyl.

Ophbalance · #5 08-16-2008, 04:02 PM

I've had the same experience as lamebums in my 4 banger Elantra. The hit on the engine from running the compressor outweighs the hit of an open window even at 65 MPH.

psychojuggalo17 · #6 08-16-2008, 04:37 PM

i dont have a sg to test, but i usually have my window open. if im alone on the interstate, itll b halfway r less at 55mph w/fan, but with passengers ill have my window all the way up because passengers = # of windows rolled ALLLLL the way down! it kills me! and its hard to hear the treble in the music...

lamebums · #7 08-16-2008, 08:54 PM

Quote:

Originally Posted by psychojuggalo17

i dont have a sg to test, but i usually have my window open. if im alone on the interstate, itll b halfway r less at 55mph w/fan, but with passengers ill have my window all the way up because passengers = # of windows rolled ALLLLL the way down! it kills me! and its hard to hear the treble in the music...

I'll take having all the windows down over the A/C anyway. And if you can't hear the music over the road, crank it up further.

This is coming from a guy who's completely deaf in the right ear and believe me when I'm driving all I hear is the road. Erm...and the music over it.

juglo-j · #8 08-17-2008, 01:42 PM

Don't know if anyone else's car does this, but when I hit the engine kill button I have installed on my shifter, the fan kills with the engine. When I hit the start button on the shifter, the fan resumes along with the engine. It is also kind of nice because it doesn't sit there and drain my battery when I am sitting/coasting with the engine off!

As for running the A/C I won't do it unless the fam is in the car with me or else it has to be pretty dang hot and miserable!

psychojuggalo17 · #9 08-17-2008, 08:09 PM

Quote:

Originally Posted by lamebums

I'll take having all the windows down over the A/C anyway. And if you can't hear the music over the road, crank it up further.

This is coming from a guy who's completely deaf in the right ear and believe me when I'm driving all I hear is the road. Erm...and the music over it.

lol well, trust me, its completely audible with two windows up, but its hard to hear with wind roar coming from all 4 windows lol, and i listen to my stereo where it is just below audible distortion. the bass makes it hard to hear the treble too, that probably stifles it more than the treble, but 2 12"s will do that lol

Right Lane Cruiser · #10 08-16-2008, 06:07 PM

AC? What's that?

I usually will have the windows down under 30mph (depending upon wind, might not even do it then) -- otherwise I've got the windows up and the fan blowing vent air on me. I've not voluntarily fired up AC in 2 years. I'll do it for my wife and I did try it out on the way back from the WFEC for Laurie (in the Insight). The hit on highway numbers was less than I expected by fair margin, actually.