Overdrive (typically denoted by "OD" on the gear selector) uses a higher gear ratio, resulting in lower engine RPMs at higher speeds. This improves fuel economy and reduces engine wear. However, in situations demanding more power, overdrive can cause the engine to lug or struggle. Therefore, it's best to disengage overdrive when:
* Towing: The extra weight requires more power.
* Climbing steep hills: The engine needs more torque to maintain speed.
* Engine braking: Disengaging overdrive allows for more engine braking on downhill grades.
* Low speeds: Overdrive isn't necessary at low speeds and may cause the transmission to shift erratically.
For normal highway driving at moderate speeds, using overdrive is beneficial for fuel efficiency.
