Windows down or AC?

8) Had they been driving an 04 or 05 Prius with our electric A/C they would have seen the difference........

Ben

 

actually i did run limited tests on this very theory and it does appear that the air conditioning will use up about 2 mpg over windows up air off. (the air on tests were done during the hottest period we had all summer with setting at 70º and in daylight driving only. a sidelight to this, i noticed that the headlights seem to affect gas mileage too although not as much)

but the open window thing was much tougher to figure out. there were times when the window open didnt seem to matter. and i found that one window open at speeds up to 40 mph also didnt appear to affect gas mileage much.

i will pursue this a bit more when the weather is better because a lot of the data i have is inconclusive and what data i do have that appears consistant i want to verify again. i had what i thought were real differences but someone pointed out (correctly we determined) that only side by side comparisons on distance, route, and direction would lead to good data.

i found that wind direction especially in areas where a breeze is nearly constant and in same direction. (this explained a 2+ mpg difference in round trip legs)

 

Personally, I'd rather have the AC on and windows up, regardless of how it effects MPG. I'm sick of roasting in my no-AC Blazer. Windows down doesn't do squat to cool me once the temps go above 75 degrees. *made SURE to have AC when ordering her Prius* AC is the best thing ever invented for cars. B)

 

well Star you are in luck... cant get a Prius without it

 

i just saw the same Mythbusters show and the window down SUV did go an extra 30 laps (15 miles) on only 5 gallons of gas. that makes an additional 3 miles per gallon which tells me they screwed up somehow.

if the SUV's got 11 something then a 3mpg difference would be over 25%.

something aint right here and im very surprized that they didnt question the results more than they did, although they did express their surprize at the unexpected results.

i will say that the slower you go the less the windows open will affect gas mileage and the Prius will be affected differently to simply because of the way the air conditioning is produced. its thermostatically controlled so temp will make a difference too.

 

It would be interesting to see how the Prius would be affected by this. Like Dave said, it would depend on the speed of the car, plus I think the outside temperature, wind speed/direction etc.

From personal experience I can say that on a straight road at around 20 °C and 80 km/h (88 on the speedo) I can see the difference in mileage when I lower all four windows, but can't notice any difference using the aircon (set @ 18 °C). Not totally scientific, I know.

Plus even if using the aircon is worse for my mileage than windows down, I'll prefer to stay 'cool and dry' instead of 'deaf and sweaty'.

 

so do i ... but we have a good two months in the fall where its too warm to not have air if the windows is up but at the same time, a window open works very well (outside temp at 55-70... sounds cool enough but with a sunny day, it can get very warm inside!!)

the window besides providing more than enough cooling power also gives one more exposure to the fresher than normal air experienced around here. because of inversions and wood smoke etc. the best air here is always fall and spring... spring has a lot of allergy components so fall is best. that is why i like the window open... plus i noticed that my car still has the new car smell to it...another reason why i like the window open

 

What they failed to question was the difference in speed. Wind drag is less of an issue at lower speeds, which is where the variance in their results came from. With the lower speeds, the power that the A/C draws off of the engine became more prevalent. With the higher speeds, the air drag on the open windows offets the power drag from the A/C compressor.

On the highway, I keep my windows up, and let the climate control do it's thing. I still avoid the A/C if the outside temps permit. In town, I open the windows up, provided the temps aren't in the 90's or more.

I wanted to question this test on the chat last night. Unfortunately, I had an unwanted date with the alarm clock, so getting a quick turn in the very loaded chatroom was not going to happen.

 

• 
  I tend to believe the second test more. In the first test, they drove 15 laps at perhaps 2 miles per lap, using about 2.6 gallons of gas. If there's an uncertainty of 0.1 gallon in filling the tank (auto shutoff of pump), that's a 0.1/2.6=4% error in MPG or 0.4 MPG error, so the difference between 11.3 and 11.8 MPG is not very conclusive. In the second test, they probably drained a 25 gallon tank so 0.1 gallons of uncertainty in the fill corresponds to 0.4% error in MPG.

 

I know. Isn't that awesome? :mrgreen: :clap:

 

well i think its safe to say that there is a mid point where it becomes more economical to run the air conditioning. it seems to be right about 40-50 mph range.

i will be running tests later as weather permits. another thing that isnt a mileage concern, at higher speeds the additional wind is more a pain than anything. anything loose in the car might blow out the window, etc.

although it hasnt happened to me in years, i did once get hit in the face by a bumblebee once that made my eyes water so bad i had to pull over. that happened in the nevada desert on the way back from vegas at 80 mph...

 

Sounds like Fear and Loathing is called for! A friend of mine who was bicyling once got stung on his wagging tongue...

 

wasnt that a title to a movie...."Fear and Loathing in Las Vegas"?

 

:rofl: My father was riding his Harley and had a bee hit him in the chest. Went down his shirt and he nearly had an accident when he paniced! I have also had a bee do the same to me.... my Blazer's windows were open and the bee blew in. Felt like I got hit with a rock. I've never pulled over so fast in my life. Luckily the bee was stunned so I could flick him out the door. I was so afraid it would get pissed off and sting me. :lol: