I *like* my cruise control. When I’m driving for 8-9-10 hours at a time, the reduced fatigue using the cruise control is well worth ANY claimed (marginal) “increase” in fuel use experienced.
I do agree that using it on hilly or very curvy roads is not as efficient as allowing the car to gain and lose speed as the road profile demands.
Actually, I have not noticed any increase in fuel usage with the cruise control, but I’ve been driving only 35 years. Using it on the prairies I have gotten over 30 MPG in my 20+ year old V-8 Crown Vic.
Hyper-milers may not use cruise, but they tend to ignore MANY rules of the road as well in their quest to squeeze every last inch of distance out of their fuel. Do a search on their websites and see how inconsiderately they use the road. You’ll likely never reference them again when making a post about driving, since they are often more dangerous than drunks.
Actually cruse control saves money! Set it at the highest rate you can run without getting tickets. Tickets cost a lot more than any fuel savings and tickets are going up faster in cost than gas.
On flat straight roads there is only “marginal” difference but on hilly and curvy roads the difference can be major. I have owned a 1985 Crown Vic, a 1991 Crown Vic, a 1996 Crown Vic Police Interceptor and currently have the Mercury Grand Marquis 2004 model which is of course the same car. The best mileage I ever got with cruise control was 28 mpg traveling southbound on I-95 which was not hilly, it was close to flat. The best I ever got WITHOUT cruise control was 31.4 mpg with the Mercury driving in very hilly country, some of it almost mountainous. I call that more than a marginal difference. Simply put cruise control is NOT a gas saver in reality. If you prefer to use it fine, you will get no argument from me, I just want people to stop kidding themselves that using cruise control gives maximum mpg.