Does using a/c in my car use more gas? i think not?

i got in an argument with my mom. i'm trying to convince her that the a/c in a car doesn't use gas when it's turned on. the car has to spin the serpentine belt no matter what, which will spin the belt for the compressor for the a/c no matter what. so no matter what, if a car is equipped with a/c it's still using the same amount of gas imo. whether the a/c is on or off it doesn't matter because it still has to spin the belt. if you remove the whole a/c system then you could increase hp and increase gas mileage in my opinion.





i also told her having the windows down would use more gas....i couldn't convince her...what you think?

Does using a/c in my car use more gas? i think not?
The front of the compressor is constantly being spun by the serpentine belt, but it is a matter of wether or not the clutch is engaged on the compressor. When the clutch is engaged, the compressor puts a load on the serpentine belt, thus putting more load on the crankshaft. The increase in load lead required more power to maintain the desired engine speed from the driver to maintain a certain speed. This increase in power requires more fuel.





It is not a substantial amount of extra fuel needed, but it is better to use the A/C when driving down the freeway. Leaving the windows open at high speeds, increases the drag of the vehicle. Then the whole problem with increased load on the engine comes into play again.
Reply:it does effect the gas mileage if the air is on. it takes little more h.p. to turn the belt with the air compressor on, however if the windows are rolled down in the car,the drag created would probably burn more gas than the air conditioner.
Reply:The compressor isn't working if you don't have the ac on, so it is using more fuel in that sense if you turn the AC on. If you roll down the windows instead of turning on the AC supposedly that produces as much drag as running the compressor. If you want to save an ounce of fuel, sit in the vehicle and sweat it out. Otherwise use about the same amount of fuel to roll down the windows or turn on the AC.
Reply:the ac compressor has a magnet clutch on. when the ac is off it has no pull on it.with the ac on the magnet clutch ingages the ac compressor and turns it and takes about two to five horsepower to pull the ac compressor and that uses more gas. you do get less gas milage with your windows down.
Reply:The a/c compressor has a clutch on it. When the a/c is off, the clutch lets the pulley turn without running the compressor. As far as mileage goes, in city driving it uses more fuel with a/c running. On the highway the aerodynamic drag from open windows uses more gas than running the a/c.
Reply:It's about the same either way. Be comfortable, the amount of fuel is not significant.
Reply:even though the serpentine belt does indeed turn the a/c compressor unit pulley when the engine is running, it has a form of clutch which engages when the a/c is switched on, which creates some drag on the engine, this will create more drag on the engine and thereby could increase gas consumption.
Reply:When the A/C is turned on the clutches on the compressor kick in. If you tried to turn the compressor with your hands, you couldn't! Driving the compressor takes alot of power from the engine. That's why there is a throttle step-up switch that kicks the throttle up when the A/C is turned on. So, yes, it does burn more fuel and it does rob horsepower. Other accessories like the alternator and power steering put a drag on the engine, just not as much at the A/C.


As far as the windows down...it does screw up the aerodynamics of the vehicle, but increased fuel use would be trivial.
Reply:As far as I am aware a/c does use more fuel when on in a car.
Reply:Yes the A/C will cost you in more gas. Why? Because the motor is working harder to drive the compressor. The compressor is electric operated through the plug-in you see at the rear of it or at the front of it. Once activated the compressor relies on the car motor to turn the belt to move the cool air into the cabin. Until the A/C is switched on inside the car the pulley the belt is turning is free-wheeling.
Reply:i always heard that it used more gas
Reply:Your mom is correct. It places an extra load on the motor. Though the belt does spin, when the AC is off, the clutch is dsengaged.





When it is engaged, it adds drag.





The windows could go either way and is predicated on the body style of the vehicle.





Trucks with tail gates down reduces a vortex of concentrated air turbulance at one spot and spreads it over a larger area, thereby increasing drag and costing more gas consumption...