Does A/C affect MPG?
Senior User
Joined: Nov 2010
Posts: 173
Likes: 0
Anything that requires power to operate will effect fuel mileage.
How much is always the question.
A 2 liter engine will take a larger hit than a big loafing along 460.
My 460 consumes so much fuel that I see no difference ac on or off but it has to be something because the power it takes to operate the compressor and fan as well as the added heat load to the cooling system has to consume power.
How much is always the question.
A 2 liter engine will take a larger hit than a big loafing along 460.
My 460 consumes so much fuel that I see no difference ac on or off but it has to be something because the power it takes to operate the compressor and fan as well as the added heat load to the cooling system has to consume power.
Postmaster
Joined: Jan 2012
Posts: 3,462
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From: Richmond
There was an episode of mythbusters where they drove two explorers around a track at a constant speed. One with windows, one AC. No difference between them. But that is just a small part of the story. Acceleration is a killer. I used to drive a car with a 6L v12. Full blast AC with two compressors made no difference on accel. or mpg. But like oleman said, mpg was so bad that it didn't matter.
Friend of mine drives a 4cyl camry. He used to have a sticky note on his AC button that said TURBO
My current DD is a 6cyl. When it's very hot the ac makes a little lag on the engine. But, it has a speed cutoff that disengages the compressor clutch when accelerating. I've got the same car 2yrs older for parts, no speed sensor. With the air running the difference in their MPG gets about 8% bigger. Not too bad, but running 93 octane over $4/gal and getting 12MPG is adds up hah.
Find out if your truck has a compressor shutoff. If it's tuned up well you shouldn't see much difference between air/windows/nothing on the highway. If you're in traffic or accelerating on a ramp try hitting the switch.
Friend of mine drives a 4cyl camry. He used to have a sticky note on his AC button that said TURBO
My current DD is a 6cyl. When it's very hot the ac makes a little lag on the engine. But, it has a speed cutoff that disengages the compressor clutch when accelerating. I've got the same car 2yrs older for parts, no speed sensor. With the air running the difference in their MPG gets about 8% bigger. Not too bad, but running 93 octane over $4/gal and getting 12MPG is adds up hah.
Find out if your truck has a compressor shutoff. If it's tuned up well you shouldn't see much difference between air/windows/nothing on the highway. If you're in traffic or accelerating on a ramp try hitting the switch.
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Hotshot
Joined: Sep 2001
Posts: 11,958
Likes: 228
I almost always agree with Subford, but I wouldn't run on the highway with the windows and slider open. From my experience it causes the headliner to start to sag. From what I can tell, there is virtually no difference between running AC or windows down on the highway. In town is a different story entirely though.
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Junior User
Joined: Feb 2012
Posts: 51
Likes: 0
From: Granbury Tx.
There was a deal on the PC the other day Fuel Myths. According to them running the A/C uses no more fuel. This was a gov. run tests. Your foot uses the most fuel lol. Todays newer engines i can belive this easily. On older vehicles you certainly hear a big diff. in motor when turning on A/C.
Running with gate down actually uses more, windows up or down didn't make much diff.
Tounua cover didn't make diff. Take this for what it is worth lol. There were more things that affected mpg can't remeber all of them. oldtimers disease lol.
Running with gate down actually uses more, windows up or down didn't make much diff.
Tounua cover didn't make diff. Take this for what it is worth lol. There were more things that affected mpg can't remeber all of them. oldtimers disease lol.
Posting Guru
Joined: Jul 2008
Posts: 1,250
Likes: 1
I agree with what everybody else has said. It does take power, but on something like the 460, the exterenal variables (ie weather, traffic, etc) makes it impossible for me to see any difference in fuel economy from tank to tank with and without A/C. My '03 Focus with the 2.0 however sees a 4 mpg hit in highway mileage with A/C and you can feel the car slow down every time the compressor kicks in.
Cargo Master
Joined: Nov 2009
Posts: 2,364
Likes: 117
From: starship enterprise
Well, I watched fuel consumption like a hawk on farm equipment and construction equipment. In winter months Vs summer months fuel consumption went unnoticed with AC on or off on the same machine. Those were diesels running at lower rpm than gasoline engines but They burned the same fuel in a 10 hour shift AC on, AC off, Ac disabled. I probably turn mine when I get hot, turn it off when its cold, and buy gas when I need to.
Lead Driver
Joined: Jan 2003
Posts: 9,893
Likes: 12
From: Ohio
Yup, big motors don't see the drain a compressor puts on them. My lil 1.9 4banger in my Escort would slow down when it kicked on. It would lose 4-5 mpg in the summer when I ran the air.
My PSD or 460 never noticed a thing. The only thing that killed mileage in those was MPH. Keeping it down at or below 65 really helped. Much faster, the wind resistance really took its toll.
My PSD or 460 never noticed a thing. The only thing that killed mileage in those was MPH. Keeping it down at or below 65 really helped. Much faster, the wind resistance really took its toll.
Cargo Master
Joined: Mar 2007
Posts: 2,935
Likes: 34
From: Arcadia, Fla
Got the A/C fixed in my 89 F250 two months ago, I have noticed only a .5 MPG drop since using A/C. That was averaged over the months before and after AC fixed. I was courious like the rest of us. A .5MPG drop for COOL air works for me. Also I can hear my radio now!
Cargo Master
Joined: Mar 2007
Posts: 2,935
Likes: 34
From: Arcadia, Fla
That won't work here in Florida, turn the AC off and the air hits you like a brick with the humidity. I finaly fixed the hard vac line to the AC recirc servo, now I can colder as the air is recirulated and the humidy is removed from the cab. Just got home and stepped out of the truck almost went back in, muggy today and its only the beginning......
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