Posted by JR Olson | Posted in Energy Conservation Tips | Posted on 06-02-2016
With the price of gas rivaling a King’s ransom, people are looking for better fuel efficiency in their vehicles. Unfortunately, the warm summer months appear to have an inverse relationship with your car’s mileage per gallon: when temperatures increase, fuel economy tends to decrease.
There are two main reasons for this: air conditioning negatively affects your fuel economy but so does driving with the windows down.
For most people, driving with neither air conditioning nor an open window is not an option; you likely want to arrive at your destination without risking heat exhaustion. So, you are left with a choice to make: crank up the air conditioning or roll down the windows.
It turns out both have their advantages and disadvantages.
Air Conditioning vs. Open Windows
The biggest advantage to air conditioning is comfort. Not only does it keep you cool on hot summer days, but it also helps regulate the noise level inside your car. In addition, using air conditioning avoids having to roll down the windows, which can actually be safer. An open window can let in insects, debris, and, on rare occasions, even birds. All of these can prove quite distracting and possibly lead to accidents.
According to Time, an open window can also increase the risk of skin cancer in the areas that are exposed to sunlight, such as the driver’s left arm.
However, using the air conditioning for comfort and safety isn’t free: per the US Department of Energy, running your car’s air conditioner on max can decrease MPGs by between 5 and 25 percent. Choosing to roll down the windows also comes with some advantages. Rolled down windows allow fresh air to be let in. And, of course, an open window exhibits the true essence of the open road: radio on and wind in your hair.
Yet, these perks aren’t free either: open windows often create an added resistance that your car must work harder to overcome, thus using extra fuel in the process.
Splitting the Difference
Like so many things in life, getting the best fuel economy for your car may involve a little meeting in the middle. Using the knowledge that air conditioning dramatically reduces a car’s fuel efficiency, coupled with the knowledge that rolling the windows down also decreases fuel efficiency by causing drag (which increases with speed), the Society of Automotive Engineers performed a study to answer one question: at what point does the fuel use caused by the drag cancel out the fuel saved by not using air conditioning? Their answer was around 65 miles an hour.
The engineers concluded from this study that cars were more fuel efficient with no air conditioning and the windows rolled down for all speeds under 65 miles an hour. For speeds higher than 65 miles an hour, cars were more fuel efficient with the air conditioning on and the windows rolled up.
Thus, when it comes to air conditioning versus open windows, the answer is simple: when you’re driving slow, roll your windows low; when you’re up to speed, it’s time for some A/C.
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