Thread: a/c helping mpg??!!

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A local shop around here put out a brochure that claims that running the air and keeping the windows up will give you better milage than running around with the windows down! Going on the idea that with windows down it creates more drag than with them up and kills the areodynamics. Does anyone think that takes more out of it than using the a/c?
personnaly, I am not buying it. I have seen the a/c take 3-5 mpg and don't think the windows being down would do more than that. Haven't really gotten that deeply hung-up on the subject but thought it would be something for us to scratch our heads about.

Don't know. Saw it on Mythbusters once, they said the same thing. Probably especially true on newer cars that actually have some aero....

Run a test: One week fill up your tank and set your tripometer to zero and see how far you go on a tank of gas. Next fillup, do exactly same thing, but ride around with the windows open, no A/C.

Let us know how you make out.


Don

I've heard that story for thirty years or more, didn't believe it then and doubt it now. With the new, gutless little pointy-ended 'boxes they call automobiles these days, and tiny Chinese compressers, it might actually be true. Hope I never have to find out!

Originally Posted by burrbrian

A local shop around here put out a brochure that claims that running the air and keeping the windows up will give you better milage than running around with the windows down! Going on the idea that with windows down it creates more drag than with them up and kills the areodynamics. Does anyone think that takes more out of it than using the a/c?
personnaly, I am not buying it. I have seen the a/c take 3-5 mpg and don't think the windows being down would do more than that. Haven't really gotten that deeply hung-up on the subject but thought it would be something for us to scratch our heads about.

newer cars i'd say its so.

Originally Posted by lt1s10

newer cars i'd say its so.

I agree, the newer A/C systems are much more efficient. Even the newer trucks are designed with aerodynamics and are most efficient with the windows up.

Pat

I drive 120 miles a day to work and back. I drive either a '92 Astro Van or a 2000 Monte Carlo SS. I can definetly say I get better mileage with the windows up and the air on. My '95 GMC Sierra is the same way and so was my '89 Chevy pickup. You won't get any argument from me that there is a difference...
Mark

The newer a/c compressors don't drag on the engine as they did back in the 60's and 70's, they take away very little hp. If the car is relatively drag efficient, then a/c and windows up would be more fuel efficient that no a/c and windows down. Now as for old cars and cars using the compressors that take a toll on the engine or less aerodynamic vehicles, then the efficency would be less likely. This does not apply to street rods and kustoms though. If you truly want to be cool in one of these cars, you gotta open the windows and hang your elbow out while wearing your shades and a tee shirt.

If you can't be Milner, at least you can pretend.

I agree with Denny. In stop and go traffic gas mileage will suffer, but as Denny said cruisin' down the interstate at 60 mph you'll get better mileage with the ac on and the windows rolled up. Pickup trucks with the tailgate up and no bed cover will also cut your mileage cruisin' down the interstate at 60 mph.

Why not go real cheap and leave the windows up with no air conditioning? Show a little backbone, tough it out!

Hey, everybody. Seems like the general train of thought is that it will get better mileage but like mopar and pope say I prefer to hang my arm out and have the fresh air in my face! Never could stand being closed up with the car-or truck, in my case- shut up tight. Even run the window 1/3 way down in winter. NOT totally crazy, though. I still use heat. Thanks for everybodies thoughts on this, made for good exercise for my noodle. see ya!

Originally Posted by NTFDAY

I agree with Denny. In stop and go traffic gas mileage will suffer, but as Denny said cruisin' down the interstate at 60 mph you'll get better mileage with the ac on and the windows rolled up. Pickup trucks with the tailgate up and no bed cover will also cut your mileage cruisin' down the interstate at 60 mph.

tailgate down cuts gas mialage. with the tail gate up, there is a wind force inside the bed up to the top of the cab ( caused by a vacume at the base of the cab in the bed ) that causes the passing air to be forced above the cab and helps areodynamics, with the tailgate down, this wind force is gone, and causing it to lend no help to the aerodynamics. saw this 1 on mythbusters too. they used a model of a F150 in a small wind tunnel.

Mythbusters notwithstanding, any pickup I ever had would go at least 5 mph faster with the endgate down. Burrbrian, just because you use heat with the window down doesn't prove yer not totally crazy, I always open my window even at -40, and I AM totally crazy.

I saw that episode too Matt and in theory that is fine, but in practical application it doesn't work. I keep a running gas mileage log on all of my vehicles and every truck I've had the gas mileage has suffered with the tailgate up.

Ok, I ran a little test coming home from work today. I have a long stretch of straight road where the speed limit is 55, so I set my cruise control at 65 ( ) and with my windows up my digital infomation center on the dash was reading 18 mpg. I then rolled down the front two side windows all the way, and it dropped to 17 mpg with no other change except that I turned off A/C with windows down.

So I guess in my car at least it does make a difference. Mine is a mega pound Crown Vic with the aerodynamics of a brick. So maybe in another car the results would be different.

It also messed up my hair...............all 5 of them.


Don