when do you drive in drive and when do you use overdrive?

 

We've discussed this before as well.

Basically, OD is for everything but when you find that the transmission is constantly hunting for the right gear. If it is continuously shifting back and forth between 3rd and 4th, then you should drop it down into 3rd until you get to more level terrain.

 

I use O/D unless I'm towing, then I use "D".