Does Cruise Control save Gas even on a loopy, hilly highway?

Yes it does. Myth busters did a show on the very same thing.

no going up hills even small ones causes the car to speed up
using more gas

I do not believe so. I have found that I can beat my cruise control by 1-2 mpg on hilly terrain by accelerating gently on the downhill zones and then maintaining my throttle position climbing the hills, sacrificing vehicle speed. It’s easier to gain vehicle speed on flat ground or downhill, you should NEVER be increasing vehicle speed going uphill. I see this all the time on the highway and it makes me sick.

The cruise control will maintain the preset speed until it reaches the bottom of the hill, when the car will slow slightly then begin applying more and more throttle to maintain your preset speed. Usually on a big hill the transmission will downshift, the engine RPM will increase, and you are using a lot more fuel.

yes if you have sufficient power to pull it up hills, If you have a civic like I do, then the rpm climbs unreasonably. So no it doesn’t help me.

No, cruise control is best on relatively flat highways. Big hills force your can to down shift into passing gear, most likely 3rd, which makes your RPM’s jump from about 2000 to 3000-4000, working your engine twice as hard = twice the gas. I’ve experimented with my mother-in-law’s expedition which has a instant mpg display, and it is definitely better to go up a hill without the cruise control.

I use cruise all the time but I’ll take it off when I am about to go up a large hill, small hills I don’t worry about.

It does for most people, but if it’s done right you can save gas without the cruise control on hilly roads.