in my car it doesnt say "OD Off" unless i turn off overdrive, but i always have overdrive on 100% of the time.
i guess a newer car might turn OD Off if you ARE going uphill, and youre right there at a constant speed right about at that sweet spot where it would normally try and switch gears, to prevent the car being balanced right there for an extended time. but unless you're going up like a ten mile long hill at a constant speed of 35 mph, overdrive should always be on
just leave it on 100% of the time, turning overdrive off will fuck your car engine if you try and hit the freeway doing 65mph in 3rd gear cause your OD is off
and wtf you couldnt figure this out after like four years? lol