Since I have been running avgas in my strokes, I havent had a single problem. Yeah, its 100 octane leaded fuel, but its very tightly controlled for consistency and purity. I store all equipment with full tanks, and no additives. Avgas has a 2year shelf life, so it wont turn to varnish nor introduce alcohol or water into the system. Years of doing this, and have never had a single problem, running, starting, or otherwise.