O/D on or off
Should I drive my 2018 Nissan Sentra on O/D
or turn it off if I’m only driving around town?
Most people just put the shifter in the highest gear whenever they drive; then you don't have to think about it. But for people like you and me, the slower you drive, the lower the gear you should use. I actually shift through gears to set speed or help in braking. An automatic transmission really doesn't care which gear it's in; they all run all the time and it's the bands and clutches that determines which is engaged. If you're going at a top speed of around 40, just use the gear under the top overdrive.