settle an old rumor regarding A.C usage

Winger98

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Is it true that AC use in a car leads to burning more gas? My local mechanic said 'it could go either way' but would rather get a better explanation elsewhere lmao.

I have a 2014 Honda Civic

The only way I have understood this to be true is that under 50 mph it takes more gas to run the a/c than to overcome the drag from opening the windows. Over 50 mph and the drag from opening the windows becomes greater than the work put in to run the a/c. However, if you're moving 10 mph in crappy traffic from stop light to stop light then sitting their with the windows open isn't really comfortable. but it feels alright if you're going 65 don't the highway. So, yeah.
 

Rodgerwilco

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The only way I have understood this to be true is that under 50 mph it takes more gas to run the a/c than to overcome the drag from opening the windows. Over 50 mph and the drag from opening the windows becomes greater than the work put in to run the a/c. However, if you're moving 10 mph in crappy traffic from stop light to stop light then sitting their with the windows open isn't really comfortable. but it feels alright if you're going 65 don't the highway. So, yeah.
In summation, it looks like "it could go either way". lol
 

TaLoN

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Is it true that AC use in a car leads to burning more gas? My local mechanic said 'it could go either way' but would rather get a better explanation elsewhere lmao.

I have a 2014 Honda Civic
In summation, it looks like "it could go either way". lol

Both trying to cool the inside of the car by rolling down windows or running the AC lowers fuel efficiency. One doesn't lower it much more than the other though.

Car Myth Debunked: Does Running the AC Use Gas?
Which is More Fuel Efficient?

There are multiple factors that affect your car’s fuel efficiency, but the answers to these questions might surprise you. Using the AC in your car does lower your car’s fuel efficiency by an average of 3 miles per gallon depending on the age and size of your car. AC lowers your fuel efficiency because it is diverting energy from the engine to power the car. The fuel to power the AC has to come from somewhere, and the engine is the most efficient way for the AC to get its energy.
If you’re driving at high speeds, leaving your windows down can actually lower your fuel efficiency more than using your AC would. Lowering your windows can lower your fuel efficiency because the wind entering your car creates a drag that forces your car to work harder to get to the same speed if the windows were rolled up.
The Bottom Line

Regardless of whether you choose to use the AC or roll the windows down, there’s no method to cool your car that doesn’t lower your car’s fuel efficiency. Choose the method that makes you the most comfortable while driving. A car that is too hot can lead to drowsy or distracted driving, which can eventually lead to a crash. Both options lower your vehicle’s fuel efficiency, but not by enough that you shouldn’t use either method to cool your car, especially during the summer.
 
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ProstheticConscience

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Is it true that AC use in a car leads to burning more gas? My local mechanic said 'it could go either way' but would rather get a better explanation elsewhere lmao.

I have a 2014 Honda Civic
The greater the electrical load you put on an engine the harder the engine has to work to keep the car moving. That's why your gas mileage goes down when you run the A/C. Ever notice how your car kind of shivers and clicks and doesn't idle as high when you put on the A/C? That's why. A/C takes a lot of juice to run.

No idea what your mechanic thought when he said "go either way". There's no either way about this. Opening all the windows and creating a wind tunnel in your car in an interesting interpretation. Can't really see it being all that more efficient, you drive with roaring wind noise and you emerge from your car looking like you just spent an hour being sandblasted. Also you weren't as cold if you'd just turned on your A/C like a normal person.

Find a mechanic who knows what he's talking about, and gj on the car. I've got a 2013 Civic Si. Great car.
 
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HansonBro

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The greater the electrical load you put on an engine the harder the engine has to work to keep the car moving. That's why your gas mileage goes down when you run the A/C. Ever notice how your car kind of shivers and clicks and doesn't idle as high when you put on the A/C? That's why. A/C takes a lot of juice to run.

No idea what your mechanic thought when he said "go either way". There's no either way about this. Opening all the windows and creating a wind tunnel in your car in an interesting interpretation. Can't really see it being all that more efficient, you drive with roaring wind noise and you emerge from your car looking like you just spent an hour being sandblasted. Also you weren't as cold if you'd just turned on your A/C like a normal person.

Find a mechanic who knows what he's talking about, and gj on the car. I've got a 2013 Civic Si. Great car.

It's not an electrical load. A/C runs off your serpentine belt. The a/c pulley is always spinning, but until you actually turn it on, it's not engaged. Pop your hood and try it. Have someone else turn on the a/c and you can see the clutch move

The extra load on the motor comes from the clutch being engaged. During city driving it may effect mileage but doing highway miles its hardly noticeable
 
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ProstheticConscience

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It's not an electrical load. A/C runs off your serpentine belt. The a/c pulley is always spinning, but until you actually turn it on, it's not engaged. Pop your hood and try it. Have someone else turn on the a/c and you can see the clutch move

The extra load on the motor comes from the clutch being engaged. During city driving it may effect mileage but doing highway miles its hardly noticeable
Huh. Been a long time since my auto mechanics classes in high school.

But @ OP: a/c does use about 4 hp to run, so yes, it does decrease fuel economy just for draining power.
 
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islandersbob

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It's not an electrical load. A/C runs off your serpentine belt. The a/c pulley is always spinning, but until you actually turn it on, it's not engaged. Pop your hood and try it. Have someone else turn on the a/c and you can see the clutch move

The extra load on the motor comes from the clutch being engaged. During city driving it may effect mileage but doing highway miles its hardly noticeable
Do all cars have serpentine belts now? I remember one of my dad's old 80's junkers, had multiple belts coming off the crank. The car had a compressor, but he just removed the belt. I know he was obsessed with gas mileage for a while, but I don't think that's why he took the belt off.
 

HansonBro

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Do all cars have serpentine belts now? I remember one of my dad's old 80's junkers, had multiple belts coming off the crank. The car had a compressor, but he just removed the belt. I know he was obsessed with gas mileage for a while, but I don't think that's why he took the belt off.
I would think yes on all gas/diesel motors. No idea about the electric cars.

I know on my 2001 Tahoe there is an auxiliary belt just for the A/C. Maybe that's what your dad took removed. Ironically, mine chewed itself off
 

TD Charlie

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In general, yes it uses more fuel for reasons already explained.

Life is too short to be uncomfortable. If you're hot, crank that shit without a care.
 
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Baby Punisher

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In summation, it looks like "it could go either way". lol
Exactly.
I have driven convertibles all my life. I see very little difference with the top up and A/C on, or with the top down and A/C off in any driving conditions. When I have the top-down and the A/C on I do see a drop in fuel economy. I don't drive cars for their effeciency. I do enjoy the good gas mileage when I get it. I unabashedly drive cars with big v8's. If any of them achieve 15/25 I am thrilled.
 
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