The myth about air/heat and gas!!!

[stilts07]

Everybody keeps telling me something different! some people telling me heat dont use more gas but air does, or air conconditioning uses more gas when you have it on. Other people told me neither uses any gas?? What is the truth???

[KiwiBacon]

The heater in your car doesn't use any engine power (well other than electrickery to drive the fan). The heat would be pumped out through the radiator if you didn't put it into the cabin.

Air conditioning does use more fuel, the compressor which drives it is driven from the engine crank.

[zudo]

Originally Posted by stilts07

Everybody keeps telling me something different! some people telling me heat dont use more gas but air does, or air conconditioning uses more gas when you have it on. Other people told me neither uses any gas?? What is the truth???

Both cases you stated are saying the same thing, that air conditioning uses gas.

[UncleBob]

some cars are so aerodynamic that at freeway speeds, you get worse mpg with the a/c off and the window's down vs the a/c on with the windows up

[KiwiBacon]

Originally Posted by UncleBob

some cars are so aerodynamic that at freeway speeds, you get worse mpg with the a/c off and the window's down vs the a/c on with the windows up

That'd probably be most cars. But you can save fuel by keeping the AC off, windows up and your passengers suffering.

[Hungrycat7]

They did this on Mythbusters but I can't remember the outcome. I am pretty sure they did it with a non aerodynamic Ford Explorer though

[beef_bourito]

Originally Posted by Hungrycat7

They did this on Mythbusters but I can't remember the outcome. I am pretty sure they did it with a non aerodynamic Ford Explorer though

they took two explorers and i believe they drove at 55mph. air conditioning uses more gas on those trucks at that speed than windows down.

[KiwiBacon]

Of course windows down is only an option for moderate temps. When it gets hot (like 30 deg C and above) you need refrigeration to stay comfortable.

[Hungrycat7]

Originally Posted by beef_bourito

they took two explorers and i believe they drove at 55mph. air conditioning uses more gas on those trucks at that speed than windows down.

That's what I thought. I think that makes sense! It just takes a lot of power to run an air conditioner, house or car!

[72chevelleOhio]

On the A/C, I believe EVERY car will be different. Driving style and city/highway driving will play a big part in it too.
The best way, I would think, would be to test it yourself. Drive X amount (a tank full, a month, whatever) with the A/C on. Then drive the same amount with the windows down. See what you get. Maybe it won't be enough to make a difference at all...


.....or be a rebel and drive with the windows down AND the A/C on. Then everyone can feel "cool" when they're around you.....

[UncleBob]

Originally Posted by beef_bourito

they took two explorers and i believe they drove at 55mph. air conditioning uses more gas on those trucks at that speed than windows down.

it was even worse than that, they were doing a very small circular track that caused so much tire scrubbing the tires were constantly squealing from it

Sometimes mythbusters runs some really bad experiments. This was one of them. Their results were completely irrelevant

[curtis73]

Agreed. They needed to use four or five different models, and then use about 10 of each. Their experiment could have been flawed by a simple fuel pickup tube being a couple millimeters different in each truck, or one fuel injector out of spec.

But, it has been shown in almost all applications that A/C uses more fuel than windows down. The best way to check it on a modern car is to plug in to a real-time diagnostics program and watch the injector pulsewidth while driving in each situation. I think you'll find that putting down the windows makes little or no difference, and in fact sometimes makes a positive effect, but A/C always makes a negative impact. The A/C compressor is almost like holding the brakes a tiny bit.

[GreyGoose006]

there you go curtis.
the brakes.
its a conspiracy...
get rid of the residual pressure valves and we will all be getting 300 mpg in our hummers.
YAY!!!

[NSX-R-SSJ20K]

aerodynamic drag has the predominant effect on mpg at speeds over 40mpg and if your car is old it will have lots of drag

[534BC]

I look in the mirror at my hair style , decide if it's ok to mess it up. This determines whether or not I am willing to run with the windows down OR I have to pay the extra to run the AC and keep from messing up my hair.