It's 90° out, which will be less detrimental to gas mileage?

[b0mbrman]

Hi guys, long-time lurker/first-time poster

I'm looking at a long road trip with some less than favorable weather conditions. I imagine temperatures along the route may reach into the 90's.

Now, there are two options I can take:

1) Turn on the air conditioner to maintain a comfortable 80° within the car
2) Open the windows to let air in, but to create drag

Which will be worse for gas mileage?

Yes, the trip is long enough that I can do fill-ups testing each part, but I want to get your opinions beforehand

 

[SynthDude2001]

Hi guys, long-time lurker/first-time poster

I have no idea, but in the part of the country I live in, not using A/C in the summer is simply not an option.

Edit: Your profile says Texas too.

A/C > gas mileage, IMO

 

[Eli]

If your AC is only capable of keeping your car 80º when it's 90º outside, there's something wrong with it.. lol

 

[nsafreak]

Well the Myth Busters (Discovery channel) did a piece on just this subject. Which car would get better gas mileage one with the A/C turned on or one with the windows down. After their experiment in which they drove two identical vehicles around the track with the same amount of starting gas until they ran out of gas the one with the windows down won by a good margin.

 

[rezinn]

I've wondered about this as well. Realistically, the loss in gas mileage from A/C is negligible. With the compressor engaged I've read that it leaches something like 2 horsepower. As far as drag on the car from open windows, probably about negligible too unless your car is super aerodynamic.

The differences will be way smaller than is measurable given differences in driving conditions. I don't believe you'd really be able to determine it without controlling some variables.

I'd just turn the A/C on and go without the wind noise.

 

[TechnoKid]

In my dad's Audi, it gets about 1 mpg less with the a/c on. I try to turn it off when i drive it by myself b/c the a/c compresosr sucks up quite a bit of power/engine response. Its a 2.8 30V V6, 98.5 A6, fwd. The automatic climate control computer does a pretty good job of knowing when to engage the compressor and not to maintain the temp inside the cabin.

So, in his car at least, it doesn't make that much of a difference, so long as its cruising on the highway/freeway at a steady pace with little to no traffic. I'm sure its different with a car, say a smaller engined 4-cyl civic.

 

[McCarthy]

Varies by car and driving conditions. Stop and go in the city - open the window. Down the highway - usually the AC.

 

[Byte]

air drag doesn't matter till your over 60mph

 

[DnetMHZ]

The myth busters did this experiment a few months back... from what I recall there was essentially no difference.
And at one particular speed the car using the A/C used less gas.

 

[SouthPaW1227]

Not sweating your balls off is worth an extra $5 over a road trip. Just force yourself not to eat fast food just once, and you've paid for it.

 

[wbresson]

depends on the car, how many windows and how far down they are, for example a car already creating a huge amount of drag opening the windows isn't going to matter much

 

[b0mbrman]

Originally posted by: wbresson
depends on the car, how many windows and how far down they are, for example a car already creating a huge amount of drag opening the windows isn't going to matter much

Uh...'93 Prelude...as many windows and as far down as it takes to get comfortable in the middle of June.

 

[Zenmervolt]

On the freeway and not changing speed, the A/C is more efficient.

In town, with lots of start and stop, windows open is better. A/C takes very little to run when at a constant speed, but it's a big drag when accelerating since it tends to carry a lot of momentum.

ZV

 

[Zenmervolt]

Originally posted by: nsafreak
Well the Myth Busters (Discovery channel) did a piece on just this subject. Which car would get better gas mileage one with the A/C turned on or one with the windows down. After their experiment in which they drove two identical vehicles around the track with the same amount of starting gas until they ran out of gas the one with the windows down won by a good margin.

No such thing as two identical vehicles. Even mass-produced engines have variance from the factory of 5%-10% when new. And Myth Busters doesn't use brand new vehicles. Far too many other variables for their test to be conclusive in any way.

ZV

 

[vegetation]

Originally posted by: nsafreak
Well the Myth Busters (Discovery channel) did a piece on just this subject. Which car would get better gas mileage one with the A/C turned on or one with the windows down. After their experiment in which they drove two identical vehicles around the track with the same amount of starting gas until they ran out of gas the one with the windows down won by a good margin.

Have 100k+ worth of gas mileage data of my own to support this. 35-37 mpg with windows rolled down due to a busted AC that I didn't for a while; never could get above 33mpg with AC on (75% of the time). Always 80+ degree daytime weather where I am too.

 

[thomsbrain]

Originally posted by: nsafreak
Well the Myth Busters (Discovery channel) did a piece on just this subject. Which car would get better gas mileage one with the A/C turned on or one with the windows down. After their experiment in which they drove two identical vehicles around the track with the same amount of starting gas until they ran out of gas the one with the windows down won by a good margin.

unfortunately, their test was flawed in two key areas:

1) speed. they drove 50 MPH. WHO THE FVCK DRIVES 50 MPH ON THE FREEWAY? try it at 80 MPH and suddenly air resistance is a whole 'nother ball game.

2) A/C level. they had the A/C set to full blast the entire time. the A/C guy had to wear a parka and gloves to keep from freezing to death. clearly, no one would need this level of A/C. in fact, under most conditions, the A/C spends more time cycled off than cycled on.

every other test done on the subject shows A/C being a better alternative on the highway, and windows better around town.

 

[blurredvision]

I saw go with the A/C. I made this mistake last year traveling to Florida. I had the windows down, and everything felt fine, but when we got to a stopping point to get out of the car, my back was about stuck to the back of the seat. I hadn't even noticed that I was sweating profusely, and now I was atleast 1 shower away from doing anything that involved the public.

 

[Tbirdkid]

go buy a motorcycle, and get a mesh jacket... nothing like it.

 

[b0mbrman]

Originally posted by: vegetation

Originally posted by: nsafreak
Well the Myth Busters (Discovery channel) did a piece on just this subject. Which car would get better gas mileage one with the A/C turned on or one with the windows down. After their experiment in which they drove two identical vehicles around the track with the same amount of starting gas until they ran out of gas the one with the windows down won by a good margin.

Have 100k+ worth of gas mileage data of my own to support this. 35-37 mpg with windows rolled down due to a busted AC that I didn't for a while; never could get above 33mpg with AC on (75% of the time). Always 80+ degree daytime weather where I am too.

Interesting...Is this mostly city driving or highway?

 

[WyteWatt]

Originally posted by: b0mbrman
Hi guys, long-time lurker/first-time poster

I'm looking at a long road trip with some less than favorable weather conditions. I imagine temperatures along the route may reach into the 90's.

Now, there are two options I can take:

1) Turn on the air conditioner to maintain a comfortable 80° within the car
2) Open the windows to let air in, but to create drag

Which will be worse for gas mileage?

Yes, the trip is long enough that I can do fill-ups testing each part, but I want to get your opinions beforehand

A recumbent is best.

 

[b0mbrman]

Originally posted by: imtim83

Originally posted by: b0mbrman
Hi guys, long-time lurker/first-time poster

I'm looking at a long road trip with some less than favorable weather conditions. I imagine temperatures along the route may reach into the 90's.

Now, there are two options I can take:

1) Turn on the air conditioner to maintain a comfortable 80° within the car
2) Open the windows to let air in, but to create drag

Which will be worse for gas mileage?

Yes, the trip is long enough that I can do fill-ups testing each part, but I want to get your opinions beforehand

A recumbent is best.

k....any particular reason?

 

[WyteWatt]

Originally posted by: b0mbrman

Originally posted by: imtim83

Originally posted by: b0mbrman
Hi guys, long-time lurker/first-time poster

I'm looking at a long road trip with some less than favorable weather conditions. I imagine temperatures along the route may reach into the 90's.

Now, there are two options I can take:

1) Turn on the air conditioner to maintain a comfortable 80° within the car
2) Open the windows to let air in, but to create drag

Which will be worse for gas mileage?

Yes, the trip is long enough that I can do fill-ups testing each part, but I want to get your opinions beforehand

A recumbent is best.

k....any particular reason?

No gas. A lot cheaper.

 

[EyeMWing]

Easy, drive with the A/C on and windows down.

 

[bob4432]

A/C

 

[b0mbrman]

Originally posted by: imtim83

Originally posted by: b0mbrman

Originally posted by: imtim83

Originally posted by: b0mbrman
Hi guys, long-time lurker/first-time poster

I'm looking at a long road trip with some less than favorable weather conditions. I imagine temperatures along the route may reach into the 90's.

Now, there are two options I can take:

1) Turn on the air conditioner to maintain a comfortable 80° within the car
2) Open the windows to let air in, but to create drag

Which will be worse for gas mileage?

Yes, the trip is long enough that I can do fill-ups testing each part, but I want to get your opinions beforehand

A recumbent is best.

k....any particular reason?

No gas. A lot cheaper.

K...but then how do I get to work so I can earn money to eat?