In most cases, it is best to leave the overdrive light on, especially when driving at highway speeds. However, there are some situations in which it may be beneficial to turn the overdrive light off. For example, when towing a heavy load or driving up a steep hill, it may be helpful to turn the overdrive light off in order to provide the engine with more power.
Ultimately, the best way to decide whether to leave the overdrive light on or off is to experiment and see what works best for your driving style and conditions.
