this question has been bugging me for the longest time now.

the car is running anyways you might as well have the AC on if you want right? is the load that the AC compressor puts on the motor that significant that it would waste gas? if so wouldnt it make the most difference when the car is at idle?

anyone have any ideas or facts?

A\C steals a noticable amount of power. In other words, yes your car will use more fuel.

yeah there is like a ac clutch or something that engages when you hit the button. otherwise when it is off it is a fairly free spinning wheel, mostly at that point it is just excess weight, and something that reduces the radiator's cooling capabilities.

if u watch myth busters they busted this already yes it wastes more gas the harder ur engine works the more gas u going to use

Anytime your engine is put under load ( i.e a/c compressor on , added weight, low tiire pressure, dragging brakes etc. ) it will waste more fuel.

More energy needed to move the added burden.

but how much? is it a significant difference?

if u watch myth busters they busted this already yes it wastes more gas the harder ur engine works the more gas u going to use

but wasn't only up to a certain mph that having the windows down was better...like 50 or so...above that having windows down was worse because of the drag it created

^^ I found this to be true. For years, every weekend I would make a round trip from Ft. Bragg NC to Richmond VA. Up on friday and back on sunday. Now if there is a better way to track real milage in real time I dont know what is. And I found without question that windows up, ac on a 1-2 setting.. not freezing you out and speeds of 70mph average. got 3-4 mpg better than windows down at the same speeds. This was even clearly shown on the fuel gauge as the needle was higher by a measurable amount.

I wonder what is worse, using the a/c or parasitic drag from your windows being down..?? even your thumpin sound system uses more gas though.

...And I found without question that windows up, ac on a 1-2 setting.. not freezing you out and speeds of 70mph average....


When you use the a/c it doesnt matter what setting its on. the compressor will be on no matter what. The only setting you are adjusting is how hard the fan blows the cold air, the ac drags the motor all the same whether it is on setting 1 or 4. Anytime i put the ac on i put it on 4 and leave it on 4. When it gets too cold, i just turn the compressor of and let the fan blow cold air for a while...once it starts to heat up in the car again, i just turn the compressor back on...I do notice a 4-5 mpg difference when i do use the ac, but hey i have an NX so thats what the T-Tops are for!:D