I have a Oly 261. I have rebuilt is, always clean it and take good care of it. I mix my gas at 50:1 and have always ran it with no problems in my Echos, Stihls AND this Olympyk. Well, I was taking the gas cap off yesterday and just noticed that it says 20:1 on it. Thats crazy! I would never run my dirt bike or ANY saws at 20:1. That sounds like a waste of oil. Especially since oil now days is of a little bit better quality. I have it tuned to run at 50:1. And I really dont want to take two gas cans out to the woods. Is it necessary to run at 20:1, am I loosing power or wearing the engine faster by not running at that ratio? I cant believe I never noticed that before!