Overdrive is a higher gear ratio that allows the engine to operate at lower RPM (revolutions per minute) at a given speed. This generally improves fuel efficiency and reduces engine wear. Engaging overdrive is the typical setting for most driving situations, such as highway cruising. Disengaging it increases engine braking and provides more power at lower speeds.
Selecting the appropriate setting affects vehicle performance, fuel consumption, and component longevity. Historically, overdrive was a manually selectable option, but in modern vehicles, it is often automatically controlled by the transmission. Understanding the function and appropriate use contributes to a more efficient and controlled driving experience. It can be particularly beneficial when towing, driving uphill, or navigating challenging road conditions.