Oh great and all knowing Shaunâ€¦
For some time I have been under the impression that you should limit the use of your car air conditioner because it uses more gas. However, yesterday on the news I heard that in reality this does not work. They claimed the having your windows down creates extra drag on the car, which therefore negates any savings. What is the real story?
Also, some crazy guy in my life always insists that I leave my air conditioner on all year. The idea, I believe, is that it will produce a dry air, which is beneficial in the winter. Is there actually a benefit? Andâ€¦am I using more gas than necessary by doing this in the winter, when my windows are up? Any clarification that you can offer as a NEUTRAL researcher would be greatly appreciated as we attempt to settle this issue once and for all.
Two questions in one! How economical.
To answer the first question – the simple answer is “It depends”. What does it depend on? Speed.
You see, if you are going relatively slowly (under highway speeds), it is more economical to leave the windows down and not run the A/C. The A/C, while it doesn’t use gas itself, uses power from the engine (approximately 8 horsepower), and the production of that extra horsepower requires extra gasoline. When your car is moving relatively slowly, the extra horsepower needed to run the A/C outweighs the horsepower needed to overcome the drag from your open windows. (Leaving the windows down renders your vehicle less aerodynamic).
HOWEVER, when you are on the highway, and moving relatively quickly, the drag from having your windows down OUTWEIGHS that of the A/C unit’s operation. It’s actually better for your gas mileage to run the A/C in this case than to have the windows down. Good news for the hot highway traveler! Of course, some of us don’t HAVE A/C in their cars…
On to question 2.
This crazy guy is ALMOST right. But not quite. I’m afraid you’ll have to bow to his superior wisdom in a number of areas, but not overall. The fact is, regardless of the season, when you are trying to defrost or defog your windows in your car, the A/C is the way to go. A/C performs two operations on the air – it cools it, and it dries it. It’s the dryness that makes this the way to go. When you are trying to remove the moisture from your car windows, you will be far more successful if you blow dry air (which evaporates the moisture much more efficiently) than moist air. In fact, in many vehicles with A/C (unlike some of us who aren’t so lucky), the A/C goes on by default whenever the defogger is selected.
However, this doesn’t mean that you should leave the A/C on all the time, since you will be burning that 8 horsepower worth of gasoline. Use the A/C in the winter only when you have fogging issues. The rest of the time, save your gas by leaving it off!
Now, if that isn’t impartial and neutral…well, trust me, it is.