Stupid question about OD and D

Am I suppose to be driving in OD or D. The manual to me seems to make out that Drive gives you more power than OD, am I reading it wrong? I just want the better fuel economy not the power, is there a real big difference. Thanks

OD will get you about 2-3 better MPG, depending on the speeds you drive. You should always use it on the highway.

Thanks, I'll keep it in OD. If thats your lumina in the picture its pretty cool. Is it a special edition or something? it looks like the back doors are welded shut.