Marc, the only thing that switch does is prevent the transmission from going into 4th gear. This is useful when going up a steep grade and you need the extra engine RPM's to keep your speed up. Also helpful if you want to use engine braking when going down a long grade. The switch doesn't change the transmission shift points between the first, second, and third gears, so it makes no difference in surface street or stop and go driving. Maybe his advice is good for some other vehicle, but not yours. Keep it in O/D all the time except for the above situations.