I do not grease mine either, but one day had a bar sprocket jam with chips and stop turning. Had to remove the chain and tap the sprocket tips with a small hammer to get the sprocket turning again. When I got home, I blew it out with compressed air, but it still didn't turn freely. So I tried a shot of WD-40. After a bit of that, compressed air would really make it sing. Nowadays, I blow them clean with air and give them a shot of WD after every workday. It probably doesn't help them long, but maybe retards a little rust and gets them started clean on a new workday.