My wife calls me nuts.

I live in hot, sunny South Florida and drive my HCHII without the a/c (except when it rains) in order to get the best FE. If you strive to get the highest FE possible, you probably don't use your a/c either.

I have experimented with the windows and have found that opening both right side windows all the way and keeping the left side windows closed produces a very comfortable breeze at speeds of 20-25mph and above, even in 90 degree weather. At highway speeds, there is no 'booming'.

When stopped or at low speeds, I will open the driver's window to get some cross ventilation.

The noise level is also a lot easier on the ears with the left side windows closed than with them open.

We also own a Prius and this method of ventilation does not work well with it.

If you drive without a/c too and have not already discovered this, why not give it a try!

 

If you're opening your windows that's adding drag to the car. Real men drive with the windows up. (and die of heat exhaustion) Seriously, there has to be a trade off point whereby windows up and a little AC are one....

 

I bet that point is well beyond any reasonably safe speed on the freeway.

What I often do, wihch works amazingly well in my HCH-I on days where it is hot but not extremeley hot, is I will crack the driver's side window, and the right rear window. This creates a strong cross breeze right across my face and upper body. Running the fans aimed at the feet complements this well. At faster speeds, even having the front window open just over an inch, and the rear two-inches has the same effect as having the window all the way down at slow speeds -- with minimal of an impact on the drag coefficient (almost all of that drag is used to circulate air through the car, likely more efficient than the load from the elecrtic fan system).

There is no perceptible loss in coast-down speeds with the windows cracked in this fashion, however, engaging the AC compressor will immediately slow down the car several MPH when coasting downhill (in-gear) at around 55-60mph (enough speed for drag to be imporrant). Granted, the windows down will not be as effective at cooling the air down as the AC, but as far as circulation goes, it is much more powerful than the fan.

The main drawback to ventilation in this way is that having the windows down at all is going to let a lot of ambient noise in (I'm not talking about booming from air turbulence, just noise from other cars, tires, etc)

 

Having you windows open will allow a lot of outside dirt and nastiness in. I have had my car for almost 9 months, the only time the windows were cleaned was when I put tint on it a month or so after I bought the car. I have only had to wipe it down inside a couple times. My polarized glasses let me see any dust that builds up, but it really doesn't get dirty. Also with the a/c on recirculation, I don't get any nasty smells. I still get good mileage with a/c, I have ALWAYS used it. I plan on enjoying my 20k purchase and not punish myself in it. I do admit I get better mileage in the winter when the compressor doesn't run, but I won't let myself suffer.

You are right, around 55 mph and above is the point where running the a/c starts to become less drag on the engine than the aerodynamic drag on the outside of the car. Mythbusters found this out AFTER they tested and I don't remember the re-visit but I remember the comment.

I am not saying that you are not enjoying your car by not using a/c ... but just be careful. Under the recent events of people dying in the W & NE of heat exhaustion/stroke and dehydration, BE CAREFUL. You won't notice it creep on you. I work as a porter on a car lot in sunny FL and the cars ambient outside temps have been reading over 110 degrees daily, It can get much hotter inside the cars. I don't want anything to happen to any of our members, let alone anyone else.

 

You guys are crazy. When you need A/C, use A/C. You're not going to get any Olympic medals for best FE anyway. It's a car for heaven's sake, not a torture chamber.

 

Hey, some of us love pain! It builds character.

Besides, we wouldn't want any gold, silver or bronze medals. It would add weight and lower our FE.

 

this is a good point about the dust. The thing with the window ventilation (cracking the left front and right rears) I typically only do when I first start driving -- in order to clear the heat out of the car much more quickly than running the fans, as it is much more powerful. After that, once the car is down to ambient outside temperature, I shut the windows and run the AC if it is hot enough out to warrant it. More powerful fans, especially that would come on intermittently while the car is parked in the sun to clear the heat, would be an ideal solution.

 

I thought my wife was the only one that worried about dust!

This 'tip' was meant for enthusiast who, like me, do not use their a/c much and are looking for great green ventilation.


In any case, anyone who can afford a hybrid can certainly afford the extra $10 per tankful to run the a/c (if you get 60mpg without the a/c, and worst case, like my wife 40mpg with the a/c, you are only talking about 3-4 gallons of gas extra per tank, or about $10). It is obviously not about the money.

I get great fuel economy, and it is not affected the 'drag' at highway speeds (I only go about 60-65mph on the highway and get 60+mpg) with the windows open.

 

I get over 50mpg and run A/C whenever needed... I do not feel it poses uneccessary drag on the driveline. I understand that there may be some small reduction in mileage (5% perhaps?) , but I do know that at higher speeds, windows open definitely increase drag. Even the owners manual for the vehicle states that....

 

I follow what other's have posted and crack the two right side windows about 2-4 inches. It creates a great breeze while driving down the freeway as long as temps are 85 and below -- minimal drag as well.

Cheers!