Does putting your car on cruise control, on the highway or something, really save gas?

Yes, it can. A really good way to save fuel is by avoiding rapid acceleration and deceleration and by keeping the engine at as constant a speed as possible.

No matter how steady your foot is, you’ll always have some variation of speed when you have the cruise control off. Turning it on will ensure that the engine doesn’t have to waste gas speeding back up after you’ve unconsciously slowed down.

On flat level terrain, as is typical for many highways, yes.

On hilly terrain, cruise control may force ‘kick down’ shifts to maintain speed, while other drivers around you not using cruise control are usually slowing down a bit as they go up hills, so there may be some practical/safety issues around using cruise control through the Rocky Mountain passes and such.

Also, there are potential safety issues around using cruise control in the rain… it is possible that the cruise may add throttle enough to cause wheelspin in poor traction, and then get confused when the car doesn’t accelerate and add even more throttle causing fishtail and spin. I have personally taken a cruise control assisted 360 in the rain.

On normal flat terrain in good weather and traffic not too congested, cruise control maintaining steady speed may save you about 5% on fuel consumption.

Yes, because it keeps it at a steady RPM. If you’re driving without cruise control you always push hard on the gas trying to pass people and it makes your RPMs sky rocket burning more fuel.

Absolutely!…… This is one of the best ways to save gas when traveling on the highway……

manual

“A manual transmission is truly fantastic. I can only encourage everyone to try it out. You can pretty much determine if you want a sporty shifting (at higher RPM) or a fuel efficient shifting (at low RPM). No matter how “intelligent” automatic transmissions are, they aren’t as smart as you.”

automatic:

“If you have a cruise control and there isn’t a whole lot of traffic, you probably should use it (it will keep the speed constant and hence doesn’t need to accelerate).”