I've just always run them rich since all my folks did it. That was back when Stihl's were recommending 40:1. We've run them between 32 and 40:1 from the beginning and never had one burn up. I'm kind of stuck in that mode now. I've got some newer saws, but still use my older saws, like 30+ yr old saws, all the time. I figger if I keep it at an even 40:1, it's a little bit rich for the newer saws, and about right for the older ones so I don't have to lug around 2 different gas cans. Running rich is definitely better than running lean for saw life etc... Just wondering how old your oldest saw is and how long you've had your oldest saw guy??? It's all long term life I believe. I prefer to run rich, change spark plugs more frequently, and not have to rebuild. For a minimum of 3 months now I've been running my saws no less than 2 hours a day with 8+ hours/day on the weekends. These are 30yr old saws working all the time. I hope this didn't come off wrong guy. I just have a hard time adjusting to the whole leaner saw mixtures now...