Spring is here and with it comes warmer temperatures. Many of us like to roll down the windows and crank up the radio to enjoy the weather outside. However, rolling those windows down may be costing you money, even if you drive a fuel efficient GM vehicle.
With gas prices at all-time highs, it is important to squeeze every mile from your vehicles tank. You may think that running the air conditioner in your Chevy or Cadillac uses more gasoline than rolling down the windows, but in most cases, having the windows down creates more drag. Whether you own a sleek Chevy Camaro or a big Chevy Suburban, your vehicle has drag any time it is moving. Drag is the resistance that cars and other moving objects encounter when moving through the air at any speed. Most cars, including GM models, are developed to be pretty aerodynamic, but when the windows are down, air moves into the car instead of flowing over it causing resistance that wasn’t there when the windows were up.
Think of it like this: When a skydiver opens his parachute, the parachute collects the air inside it and causes a huge amount of drag. This slows the speed of the skydiver and lets him land safely back on the earth. Unlike the skydiver, you do not want drag on your vehicle because it makes the engine work harder.
The Society of Automotive Engineers (SAE) conducted a study that showed that driving with the windows up and the air conditioning on is typically more fuel-efficient. The SAE study was conducted at a GM wind tunnel and on a desert track. In the wind tunnel, air was forced over the front of the car and from an angle on the front like a cross wind. A full-size SUV and a full-size sedan were used in the study. Both showed that driving with the windows down negatively affected fuel efficiency by 20 percent or more versus a 10 percent decrease when the air conditioner was used at speeds of 55 mph.
There are some instances when driving with the windows down is a good idea. If you’re tooling around town at low speeds, it is more fuel efficient to open the windows and turn the air conditioner off. There is less drag when you are driving slower. As speeds increase, though,
the amount of drag also increases. In fact, the drag increases exponentially. If you are driving at 70 mph, there is four times more force on the car than when you’re driving around 35 mph. Doubling the speed quadruples the drag. According to some experts, the cut-off for driving with the windows down is around 40 mph for maximum fuel efficiency
If you want to spend less at the pump this spring rolling your windows down on city streets and rolling them up on the highway is your best bet. Choosing the best cooling option for the way you drive will help to keep you away from the gas pump a little longer and keep a little more money in your wallet.