Keep it in D if it's just for a short stop, continuous shifting from N to D for every stop is VERY damaging to the auto tranny. According to my mechanic friend, everytime N is shifted to D and vice versa the wear and tear involved is almost like a manual car shifting without pressing on the cluth! Ouch! I'm sure u all can imagine the wear n tear involved. Auto car is designed to leave it in auto so dun try to play manual style on it unless it's a really long stop.