Air conditioning and gas mileage
TECH Junkie
Joined: Nov 2001
Posts: 3,604
Likes: 0
From: Los Angeles
Re: Air conditioning and gas mileage More drag on the engine. The air compressor takes power to turn, and thus, puts drag on the engine. The car needs a certain amount of power to maintain speed or accelerate, and some will now be wasted going to the A/C.
Also, I'm moving this to external engine.
Also, I'm moving this to external engine.
On The Tree
Joined: Sep 2002
Posts: 113
Likes: 0
From: Spring, TX USA
Re: Air conditioning and gas mileage I keep good track of my mileage and I experienced a noticable couple mpg loss running mine on my first LS1. Though it seems to be less of a loss on my current car....
7 Second Club
iTrader: (5)
Joined: Jan 2003
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From: Grove City Ohio/Port Washington L.I sometimes
Re: Air conditioning and gas mileage If you are driving in town it will effect your mileage.On several long trips at highway speeds I get better mileage with the windows up and the air on.With a modern car you will see no mpg loss at freeway speeds.Example,drove to a vacation spot 300 miles away 80 mph windows down T-tops out 26mpg.Return trip T-tops in windows up air on 80 mph 30.7 mpg.Stock 2000 SS 6sp.
On The Tree
Joined: Jul 2003
Posts: 121
Likes: 0
From: Yakima, WA
Re: Air conditioning and gas mileage Heck - I live in the DFW area and run the AC continuously.
Commuting MPG is averaging 19.3-19.8. I do have the advantage, though, of a 2800 lb car, no power steering pump, and an aftermarket Japanese AC compressor that uses only about 75% the stock GM compressor. When I get the synchros fixed in 5th & 6th I figure it will jump up over 20.
Stock LS1 with 311 RWHP & 326 RWTQ
Commuting MPG is averaging 19.3-19.8. I do have the advantage, though, of a 2800 lb car, no power steering pump, and an aftermarket Japanese AC compressor that uses only about 75% the stock GM compressor. When I get the synchros fixed in 5th & 6th I figure it will jump up over 20.
Stock LS1 with 311 RWHP & 326 RWTQ
TECH Enthusiast
Joined: Oct 2002
Posts: 739
Likes: 0
From: houston,texas
Re: Air conditioning and gas mileage It's too damn hot not to have it!!!**** it what's the point of having it then....on the street if you get fronted to race shut it off and go for it!..although I don't know how much drag effect the windows will have if they are rolled down....I have a convertible so it doesn't matter...I run the ac with the top down sometimes ...mainly highway though.........saving a couple of mpg by having the A/C off isn't worth it....If I was concerned about gas mileage...I would of bought a 4 cylinder!! 
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Re: Air conditioning and gas mileage I am famous for turning the air on at stoplights with the t-tops off and windows down. I dunno how people get by without it, especially when its like 90 degrees out and you got those damn leather seats. I honestly don't notice too much of a performance loss with the air on. I'm sure it hurts a bit, but back when i had my Z34 if you turned the air off while accelerating you could feel the surge of power, not really so with my Z28 at least in my experience. Stay cool brothers!!!
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From Mythbusters,
Windows down vs. air conditioning
"Urban puzzle": it is more efficient, on a hot day, to run with the A/C on and windows up than to run with windows down (b/c of increasing car's drag).
Computer-based mpg measurements:
11.7/11.8 with A/C on and windows up
11.7/11.8 with A/C off and windows up
11.3 with A/C off and windows down
So, according to the computer, it's better to use A/C with windows up.
This was too quick and easy for TV, so they decided to stage a seven hour marathon, race-til-you're-empty duel, with Jamie driving an SUV with A/C on and Adam driving an SUV with windows down. Though, once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).
Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.
Windows down vs. air conditioning
"Urban puzzle": it is more efficient, on a hot day, to run with the A/C on and windows up than to run with windows down (b/c of increasing car's drag).
Computer-based mpg measurements:
11.7/11.8 with A/C on and windows up
11.7/11.8 with A/C off and windows up
11.3 with A/C off and windows down
So, according to the computer, it's better to use A/C with windows up.
This was too quick and easy for TV, so they decided to stage a seven hour marathon, race-til-you're-empty duel, with Jamie driving an SUV with A/C on and Adam driving an SUV with windows down. Though, once the safety inspector intervened, it was no longer a seven-hour marathon, it was a bit slower (45mph instead of 55mph), and a lot shorter (only 5 gallons each).
Jamie's A/C car ran out of gas first -- Adam's windows down SUV ran for another 30 laps -- completely contradicting the computer mpg estimate. Computer estimate based on air flow into the engine, so it would appear that it is unable to properly model the difference between A/C and windows down.
Banned
Joined: Mar 2007
Posts: 661
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From: Shreveport,Louisiana
Well, don't know about my Z but my stang would shut off the compressor when you nail it. Ford said it was worth about 4-5 HP. You could actually feel the car pick up a bit when you first nailed it cruising along in 3rd 4th or 5th because it took about a second & a half to cut off the compressor. The initial surge from stomping the accelerator & a moment later a second surge as the PCM dis-connected the A.C.
If the camaro does the same thing & I'm not able to feel it, its probably because my stang was a 94 & the 02 PCM is a lot faster.
If the camaro does the same thing & I'm not able to feel it, its probably because my stang was a 94 & the 02 PCM is a lot faster.
Joined: Nov 2003
Posts: 6,216
Likes: 236
From: Wichita KS / Rancho San Diego
The conventional wisdom is that below 55mph you'll get better mileage with windows down, A/C off, above 55 opposite. Can't vouch for that empirically, but it seems to make sense.
