I'm back using a powersaw to make a living and I have always mixed my fuel at 40:1, we used to mix it richer than that when in bug country as it helped to keep the mosquito's away. I try not to let it sit around for more than 2 months, I mix up enough to make sure it get used up before that time, stihl oil is good, I recently switched to Lucas 2 cycle. In 40 years I have only burnt out 2 saws, neither because of an oil issue.
