Exactly what is overdrive and when to use it? I have it on my truck but not sure when to use it.

 

assuming u have an automatic, the overdrive button, when on, allows ur truck to shift into the highest gear. this gear is used when driving at higher speeds while using light pressure on the gas pedal. Times that u would turn it off would be if u are towing a large load or driving in mountainous areas and your transmition keeps downshifting because there is not enough power in the low end of that gear. for everyday city and highway driving, overdrive is best left on

 

Overdrive is a gear that transmits to the driveshaft a speed greater than engine speed.
Overdrive gear ratios can be in automatic and manual transmissions.