I just picked up an MS261C-M. So the service manager comes out with it after firing it up and making sure it was all set. I mention to him that a lot of guys recommend running it at 40:1 and he freaks out. " Don`t do that unless you want to destroy the saw" he says. What are your thoughts? What possible harm can it do? Obviously Stihl sticks by it`s recommendation of using 50:1.