Does Cruise Control Save Gas?

Using cruise control on the highway helps drivers to maintain a constant speed set by the driver. But does cruise control save gas?

Some experts say that by maintaining a set speed, the automotive feature outperforms the average driver in fuel economy. But others point out that a driver can do better than cruise control when on hilly terrain.

We asked AAA’s Robert Sinclair Jr., “Does cruise control save gas?” and he said he doesn’t believe cruise control is helpful in terms of fuel economy.

“From the outset, cruise control was reputed as a gas saver by maintaining a constant speed and avoiding the gas guzzling on-the-gas, off-the-gas driving style of those in a hurry,” Sinclair said. “Skeptics said ‘not true’ if a lot of hills were involved since maintaining a given speed on a steep incline would use more fuel.”

Does Cruise Control Save Gas?

Sinclair said his first experience with the feature was in 1985 following his purchase of a 1982 Mazda 626 with a manual transmission. He too wondered if cruise control saves gas but found it difficult to get an accurate analysis.

“Calculating mileage was hit or miss, relying on the fuel gauge to calculate gallons burned between full and half-full,” Sinclair said. “My mileage always seemed much lower than what the car was supposed to achieve. I noticed that in certain situations, the engine screamed to high [revolutions per minute] to get back to the selected speed. How can that save gas? Also, since cruise control is almost always used on the highway, would it make a difference if used with windows up and air conditioning on or windows down and A/C off? It was difficult to tell.”

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Sinclair said that consumers have long complained of vehicles falling short of the amount of money that they were supposed to save on fuel economy due to cruise control.

On a recent drive from Detroit to New York, Sinclair said he once again pondered whether cruise control saves gas.

“The query came to mind as the vehicle I had did all sorts of crazy things while the cruise control was activated as another new system, collision braking, intervened to supposedly prevent crashes,” he said. “The cruise control tracked vehicles in front to slow down if we got too close. It seemed to track cars in an adjacent lane, so when I changed lanes to one with no cars in front for miles, the vehicle inexplicably started breaking hard. It got so bad that I worried I was going to get hit in the back when the wayward system started applying the brakes for no apparent reason. And this saves gas? I switched the system off and drove the way my grandfather learned.”

While some might argue that cruise control improves fuel economy (a 2007 CNN Money report noted that it could save as much as seven percent), Sinclair thought otherwise.

“Having little opportunity to use it and modern systems complicated to the point of frustration, my answer would be a resounding ‘no,’” he said.

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How Cruise Control Works

Like a human driver, the cruise control manipulates the speed of the car by adjusting the throttle position, but instead of pushing a pedal, a mechanism called an actuator controls the throttle when cruise control is engaged. Both the cruise control and the accelerator are attached to the throttle with a cable. Both cables move when cruise control is on, which is why you might see your gas pedal move when cruise control is engaged.

The throttle controls the speed by regulating how much air is taken in by the engine. A small computer behind the dashboard or under the hood controls the cruise control. The computer is connected to the throttle controls and other sensors.

And of course most people know this already, but cruise control will automatically disengage when the driver hits the brakes.

Most controls have on and off buttons, as well as accelerate and decelerate buttons, which let you increase or decrease your speed by 1 mph. Some cars also have a coast button, which lets you decelerate while you hold the button down and resume your cruise speed when you release it.

Recently, automakers have also introduced what’s called autonomous cruise control or adaptive cruise control. Not only do these systems maintain a speed set by a driver, they also automatically maintain a safe distance from any vehicles ahead, braking when they get to close and resuming the cruising speed when safe to do so. Does cruise control save gas? Well, some of these features can certainly help.

But cruise control systems can vary in design quality. The true test is when the car ascends a hill. A good system will not deviate the speed of the car too much during an uphill climb and it won’t overshoot the power it needs to maintain the speed necessary, either.

The fuel economy benefits of cruise control come from the system minimizing throttle openings, like when a driver lifts his or her foot off the accelerator a dozen times during a 10 minute drive. Therefore, a cruise control system that struggles on hills is not maximizing its ability to conserve fuel. However, with different systems in different vehicles, you are likely to see different results with almost every car model you drive.

What do you think? Does cruise control save gas in your vehicle when you’re driving? Share your thoughts in the comment section below.

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