Can you use overdrive on automatic gearbox when at high speed?

Yes, you can use overdrive on an automatic gearbox when at high speed. Overdrive allows the engine to run at lower RPMs, improving fuel efficiency and reducing engine wear. However, it's important to ensure that the vehicle is designed for overdrive and that conditions are suitable, such as driving on highways without heavy acceleration or steep inclines. Always consult your vehicle's owner's manual for specific guidance on using overdrive.