Windows/AC NOT affect MPG

[Zvolen]

Browsing around on-line and came across this, thought some poeple would like to read it and see what the big bussinesses think. here is the link to the full article.
http://biz.yahoo.com/cnnm/070515/050...pf=family-home


"Windows, air conditioning - who cares?

There's the old saw that leaving your windows rolled down creates an aerodynamic drag on your car, cutting down on fuel efficiency. And there's the notion that the fastest way to drain your gas tank is by running your air conditioning.

Don't believe either one.

In two separate studies conducted in 2005, the automotive Web site Edmunds.com and Consumer Reports compared the fuel economy of both a sedan and an SUV at highway speeds with and without air conditioning and how open windows affected gas usage.

What they found was no significant difference in fuel economy in either sedan or SUV under either condition.""

[SVOboy]

This was actually mentioned in another thread. The main issue is "significant." Some people here have done their own tests with their scanguage, and the drop is usually quite dramatic (at least by my standards).

I fancy this article is a bit misleading...

[omgwtfbyobbq]

Yup... What SVOboy said. Heck, I bet most Americans wouldn't consider a 10mpg difference in fuel economy "significant" judging by how they drive.

[Bill in Houston]

Yeah, most people get about 20 mpg, and can't see a 2 mpg change, so burning 10% more or less gasoline is not significant to them.

[JanGeo]

yeah exactly - NOTE the test was Sedan and SUV not an economy car!

[Zvolen]

First off sorry if this was already mentioned.

It was my belief too that the article is a bit misleading on what it mentioned and did not mention. For instance no mention of general tune up and keeping your car in good shape but promoted turning your car off. Kind of ironic how the general public views these issues.

They also didn't mention some details about the "test" average speed and vehicle type. A significant gain to me surely would not be the same to the general public who on average get 20MPG or less in a SUV.

Oh well, interesting to say the least.

[Coyote X]

In my Camaro there is no difference at all running the air conditioner on the highway with the windows rolled up. Windows down and T-tops out I get 2-4mpg less depending on the speed. Most of that is from the t-tops being out.

I think anything with 8 cyl is not going to show as much change due to a/c running. Especially considering most engines are cammed for power so they are not really running that efficiently. I would like to see someone do a test comparing mpg vs speed for windows up no a/c, a/c on low/normal speed, and windows down. I would figure there is a speed that a/c will be better than windows down and it is probably around 60mph for most cars.

[JanGeo]

I would say that it is the speed at which the noise level starts getting really loud would be when the losses start getting greater and then you can always roll them up a bit.

[DrivenByNothing]

Engine size definitely comes into play. If you're familiar with a/c compressors and systems, you'll notice that the a/c compressor and pulley are about the same size regardless of the engine size.

At idle, most small engines increase the rpms by at least 75%. In my Jeep, I have the I6 4L motor and there's barely an increase in rpm at idle.

Highway driving is a completely different beast than city driving. You're not accelerating nearly as much. Acceleration and a/c don't get along in economy cars.


You can't throw a generalization like that on transportation (or anything else for that matter).

[Randy]

Farther down the story they say cruise control nets you 7%! Edmunds and Consumer Reports drive like most people drive, so they get bad mileage all around, and report it as such.

What's true for them is true for most, but may not be true for the serious mileage driver.

[brucepick]

Originally Posted by Randy

Farther down the story they say cruise control nets you 7%! Edmunds and Consumer Reports drive like most people drive, so they get bad mileage all around, and report it as such.

What's true for them is true for most, but may not be true for the serious mileage driver.

Yup. My 22 year old engine-idling son finds that cruise control gets him better FE. Presumably because it relieves him of the temptation to stomp on the gas any old time. He has plenty to learn re. FE but isn't toooo interested.