At low speeds, makes no diff. All the 'o/d off' does is prevent it from going into 4th. This might be useful in some situations like when you want the engine to assist in braking while descending a long/very steep hill. I generally like to keep the engine revving low, and if I need accelleration then 'apply foot fully to pedal' to downshift.... so I leave mine set with the full range of 4 gears that I paid for available .
