Q. How much does driving over 55 mph impact my gas mileage?

A. Here’s one you speed demons won’t like, but yes, driving 55 mph or even a bit slower does increase your fuel economy.

Those of you old enough to remember Watergate and the Dolphins winning the Superbowl probably remember the oil crisis of the early 1970s. Things were so bad, gas was actually rationed with odd-even license plates and red and yellow flagged stations. To help the nation cut down on fuel consumption, the Emergency Highway Conservation Act was passed and part of that was the National Maximum Speed Law.

It’s a Drag

You might feel like you’re only puttering along if you’re going 55 on the highway, but you are saving fuel. Blame physics.

Air resistance or drag is the atmosphere resisting forward movement. If you’ve ever held your arm out of a car window, you’ve felt that resistance. And you know how much more powerful it is the faster you go. That same force is at work against your car, meaning the faster you go, the higher the drag coefficient.

Modern cars are slightly more aerodynamic than their 1970s counterparts, so 60-65 mph might be the new 55. Because there are so many different models of cars, there isn’t a one-size-fits-all answer. Smaller cars save more fuel at higher speeds than heavier cars. But for most cars, the sweet spot for fuel economy is between 40 and 60 miles per hour.