We love our new 2014 Grand Cherokee Overland with diesel. My minor question is this: what should the idle rpm be? Ours is about 800 rpm, which seems somewhat high, and if I release the car on level ground in idle it moves at about 6 miles per hour, which also seems somewhat high. I would think that in city driving I would get higher fuel efficiency if the engine is running slower when stopped at a traffic light, which is why I'm asking. Thanks for any enlightenment that can be offered.