I live along the coast and have no experience yet with mountain driving in my 4 month old CMax. We will soon be taking a trip to the mountains up to 9,000 ft. and will, of course, experience significant downhill grades.
In prolonged mountainous driving, you may see the engine tachometer changing without your input. This is intentional and maintains the battery charge level. You may also notice during extended downhill driving that your engine continues to run instead of shutting off.
During this engine braking, the engine stays on, but it’s not using any fuel. You may also hear a slight whine or whistle when operating your vehicle. This is the normal operation of the electric generator in the hybrid system.
Should I keep grade assist on all the time? When or will I ever need to use L gear if using grade assist?
I want to #1) not overheat friction brakes (safety) and #2) strive for best mpg.
Edited by fotomoto, 06 August 2013 - 11:28 AM.