All my 2 stroke tools say mix 50:1. The Stihls seem to run great and clean. But I just got an Echo leaf blower and the seller said use 40:1. The manual says 50:1, but this isn't the first time I've heard the recommendation to run at 40:1 and let er smoke. I only use premium 2 stroke oil. So what the rule here? Is this smokey folk wisdom or does anyone have commercial experience where running the lower ratio mix has noticeably extended the life of their equipment? Do you run at manufacturer spec or run it smokey?