The beginning of speed control - Ford Thunderbird

For the 1964 Ford Thunderbird you could order a new speed selector device. Ford claimed that motorists could save up to 20% fuel and that the system would reduce driver fatigue and lessen engine and brake wear.
Well, I wonder whether this was really true. If you really want to save fuel you actually turn the speed control off. Interesting was that the system would take control as soon as you are driving with the speed you have selected with the little wheel, different to today where you have to restart the system when you are ready.
But anyway, in 1964 this system was quite an innovation as you can imagine