Chainsaw Repair

I've always been a little skeptical of 100-1 mix oils,I know some people don't like the smoke but it's kinda like seeing how little oil your motor can run on. One day I  was able to tear down a saw that had run on 100-1 Optimol since new. Everything was really clean inside,virtually no carbon,piston looked good,but surprisingly the rings were completely worn out. I replaced the rings,and the guy also wanted the muffler modified too,so I fired up the torch to cut the muffler guts out. Well the carbon in the muffler had some unusual compound in it,it billowed really toxic smoke,it was choking me and a tough job to finish.
Is there a really bad mix oil made,yes Chevron mix oil has caused damage to several machines I had to fix,pistons blackened and rings stuck solid,and the entire exhaust system of a large outboard engine plugged solid with carbon. I think in some very small towns people have to buy what they can get at a gas station.
For High performance I like the Klotz and Bledzall oils.