General Question

mrrich724's avatar

How much does your A/C affect your gas economy?

Asked by mrrich724 (8527 points ) June 28th, 2011

What I’m specifically wondering is: Does your vehicle use more gas when you crank the A/C even colder?

Or, is it that once it’s on, it’s on, so it doesn’t matter how low or high you have the A/C?

I don’t want guesses, LOL. And if you can cite, it would be greatly appreciated.

Thanks!

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12 Answers

flutherother's avatar

You will use about 10% more gas with the A/C on. How much more will vary depending on the outside temperature and how cold you want the car to be inside.

Photosopher's avatar

Your A/C is either on or off, the compressor that is…

Turning the thermo up or down simply determines how frequently and how long it remains on or off.

mrrich724's avatar

@Photosopher I’m referring to a vehicle A/C… the kind that is either on or off… not set by a thermostat to reach a certain temperature.

Photosopher's avatar

Well that’s what the temperature control in your car does too. Same principle.

I once wired my Subaru with a separate A/C compressor switch under the dash, allowing me to turn it on or off at will, rather than wait for the thermostat to kick it on or off. It was cheaper to do that than replace the broken thermostat.

Neizvestnaya's avatar

I get a few miles less per gallon in the hot weather but we have over 100 degree days so the inside to outside difference is huge.

Aethelflaed's avatar

Yes, it uses more gas. However, rolling the windows down creates a drag, forcing the car to use almost as much the same amount of gas as it would with the AC on, windows up, and no drag.

Tropical_Willie's avatar

Highway speed with window up, 10 to 15 percent. With no A/C.
@Photosopher I can shut off the compressor.

boffin's avatar

Newer cars are designed to get better mileage with the windows up and the A/C on. Rather than having the windows down and traveling at Highway speeds.
Plus the modern compressors are much more efficient than the those from a couple of decades ago. Not to mention the cooling systems are better, which let’s you have the air on in stop and go traffic with little or no harm to the engine.
The fuel economy gain loss is almost negligible. It’s your right foot that determines the cars actual mileage.

kourkoubini's avatar

Using A/C burns more fuel BUT except for the window comparison that many guys here said and is correct there is also something else very important to remember.
Using A/C when going fast-high revs makes almost no difference in fuel consumption.
Using A/C when going slow 1st-2nd-3rd gear and such speeds makes a big difference in fuel consumption.
So Remember…use A/C when on highway but do not use A/C when in city

SpatzieLover's avatar

Hypermilers do not use a/c for better efficiency. We notice at least a 10% decrease in efficiency when using a/c with out Prius.

DelfinAshley's avatar

You will loss about 10% to 15% more gas. because to turn the air conditioner pump The motor needs to function harder . At the same time when you run the defroster to clear the windshield you are additionally utilizing the air conditioner to uproot moistness buzzing around. Generally drivers don’t know this and waste energy unknowingly by keeping defroster on.

CarQuestions's avatar

On the interstate or when driving at higher speeds, the airflow into the car with the windows down hurts gas mileage. Therefore, windows down in town, and a/c up on the interstate.

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