Originally Posted by
Carlos-Titx
Cruise control won't open the throttle fully uphill. If it did you would speed past what its set at.
Using it correctly won't make any difference to your mpg. Unless you resume it from 40mph and it was set at 70mph.
The cruise control simply opens/ adjusts the throttle to maintain its set speed - if full throttle is required (eg - up a very steep hill) it will use full throttle to reach/ maintain its set speed
In tests it made a difference in MPG (the MPG was worse when cruise control was used)