Overdrive is a higher gear ratio than the other gears in the transmission. When engaged, it allows the engine to run at a lower RPM at highway speeds, improving fuel economy and reducing engine wear. However, it might not be suitable for all driving situations.
Disengaging overdrive is often necessary for:
* Towing or hauling heavy loads: The lower gears provide more power for climbing hills or accelerating.
* Driving in mountainous terrain: Similar to towing, the extra power is needed for better control.
* Slow speeds: Overdrive isn't efficient at low speeds.
* Engine braking: Disengaging overdrive can help slow the vehicle down on descents.
In short, the switch gives the driver control over the use of the fuel-saving, but sometimes less powerful, overdrive gear.
