Daddy, here goes (sorry it gonna be long)
to drive the most efficiently you accelerate on downhills and decelerate on uphills, this way you utilise the power of the engine the most effectively.
CC works the other way round, you start going downhill and the engine backs off as you hit your required speed. then on uphill the CC pumps in more fuel to keep you at the set speed.
if you had manual control, only a very small amount of throttle opening would allow the car to accelerate quite rapidly on the downhill. meaning you don't have to use anywhere near the same fuel to get up the hill.
on a downhill when you accelerate you are storing kinetic energy in the mass of the vehicle.
example.
now if you are sitting at 60 on a flat bit of road, then you have a 15% downhill for 500m then 15% uphill for 500m.
with cc the throttle closes (may open momentarily now and again due to wind/rolling resistance) on the downhill - you remain at 60,
then the uphill the throtle opens very wide to keep you at the set speed of 60.
now manually, when you come to the downhill you keep the throttle open slightly and accelerate to say 70/75 very easily, with no increase of fuel consumption compared to driving on the flat, and then when you start going uphill you back off (not necessarily completely) and your aim should be to be back at around the 60 mark by the time you come over the brow of the hill. again hopefully not using much more fuel than driving on the flat.
All of the above can add 5-10 mpg easy, but requires alot of concentration. it also helps if you know the road. ie. if you have a small downhill then a big up hill section coming you can quietly increase your speed in the downhill section to see you through the uphill bit. and other way round if you have a small uphill followed by a big downhill section, you can afford to drop your uphill speed to say 45/50
this is my take on it all, and with the aid of an mpg gauge, which i know are not the most accurate, but you can see the direction of the trend of consumption.
thoughts?
