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I've always wondered this, and I've always heard people talking about it and arguing over it, so i'd like to know if you guys know for sure or can explain how or what not.

It does, but only slightly. Reason being, the a/c clutch only turns the a/c compressor when the clutch is engaged, and being turned by the motor and creating slightly more drag/load on the motor.

tedd

But with newer cars the AC system is more efficent.

Ive been told by numerous people in the know its better to run the air in the car than having the windows down.

I guess the drag created with the windows down is more than the small amount of drag on the motor due to the AC compressor...

Yes, newer a/c systems are more efficient, but they still do create a little drag. I noticed this when driving my mom's car (2004 honda) one day on a hot summer day. The a/c was on for most of the trip, and 30 miles from home we were well below 1/4 tank. I turned the a/c off and cracked the windows (all of them) and we still had gas when we got home.

but i guess all cars are different.

tedd

Ive heard from the Galant forums that once you exceed 55 mph the air drag from open windows causes more loss in mpg then having the ac on.

Old cars do better with the windows down, I'm talking old as in pre 80s, from a combination of their aerodynamics (or lack of) and the inefficiency of the A/C systems. Most new cars do better at cruising speed with the A/C on as opposed to windows down due to the aerodynamic design. Trucks can be an exception, though, especially if they have a sliding rear window.

Jonathan wrote:Old cars do better with the windows down, I'm talking old as in pre 80s, from a combination of their aerodynamics (or lack of) and the inefficiency of the A/C systems. Most new cars do better at cruising speed with the A/C on as opposed to windows down due to the aerodynamic design. Trucks can be an exception, though, especially if they have a sliding rear window.

im pre 80's... am i old? anyway if you ever saw the ac compressor on a mid 70's chevy vs. what they are today they were much bigger and when you started the ac you could here the rpm's drop way down on some cars. thats why everyone (myself included) used to rip the ac off. it weighed a ton and was a big drag on the motor. i had a couple cars in high school that were little 4 banger fuel savers that wouldnt idle with the ac on...

Pre-80's? Of course you're old!!!!!! haha..jkjk.

I ripped the a/c off my '75 BMW as well. I think i saved almost 50 lbs. if not more off my car. It didnt work anyway, so what the hell. Might as well!!!

tedd

The guys from Myth Busters proved that the using the a/c on todays cars actually got better mpg then with the windows rolled down because of the drag.

As far as cars go, 70s on up is is old. Pre 70s is classic, just because anything during and after the 70s sucks :) . Let's face it, even late 80s/early 90s Hondas and Toyotas are old, not because it is really that old in years, it's just that they aren't worth reviving and giving another chance, they weren't worth the first one to begin with. I'm 37, BTW. My 65 Mustang had A/C, York style compressor that ran continuously, it was ice cold, but it sucked gas too. I eventually ripped it out b/c I had bad luck getting holes in the condenser from anything and everything on the road.