use of overdrive

overdrive is for highway driving for gas milage,as far as driving in OD is totaly up to you,hope this helps.

Papa is right, OD will save on gas mileage if you are doing highway driving without a lot of stopping and starting.

That said, if you live in a hilly area or do lots of starting and stopping, I would turn OD off.  OD in hilly/start-stop conditions causes the transmission to "hunt" for the right gear, which aside from feeling disconcerting, can also sometimes cause overheating of the transmission.

When in doubt, turn it off -- said as a PA resident who drives on hills all the time, LOL.