S10 4x4 Tahoe overdrive question......
 

This is my first post and my first Chevy S10 4x4, is it more economical to drive in drive or overdrive??
I have just put it in overdrive for all driving, perhaps if I was towing something it may mean that I have to downshift perhaps??
Would the overdrive be better off for highway driving only?? I am mainly doing it for fuel economy, with the price of gas these days nobody can afford to be romping around anymore.