I port a saw almost every day and constantly have to run a saw. I put a couple tanks through a couple saws every day. I rarely cut timber anymore,I port full time and have for a very long time.
I see what poor oil at 50:1 does every day.
I've got most of my local customers switched to Walmart oil at 40:1 and I like what they look like inside. It's very good oil.
For 4.99 a quart I'll try changing them over to valvoline. I ran it to see how it was before telling them to switch, it's very good oil and very cheap. Bad gas and orange stihl are what kill the dead saws I see but even that is rare,saws are extremely tough.