Not that I need to explain myself to you, but since you apparently don't know quite as much as you seem to think you do....
I do it because I run the same mix in ALL my handheld tools, and chainsaws need the added lubrication to keep from burning a cylinder since they run at so much higher RPM's and produce much more heat than other handhelds. It may not hurt to run your saw every now and then on 100:1, but it isn't good for them if you run them a lot like some of us do. Just go ask a pro in one of the tree care forums what a cylinder looks like after running a saw on 100:1 for a while.
Originally Posted by Darryl G
I can also tell by looking back to see how they're hanging and often reach back and feel them to see how firm they are.