My first Stihl was an 029 Farm Boss. That was a great saw. I built two log cabins with it, and cut lots of firewood.
I lent it to my best friend, Bud, for a week. He returned it and it was full of gas and oil. What a nice guy.
And two days later, I cranked it up, it ran real strong for 30 seconds, and then died.
Took it to the shop. Dead. Bud had filled it up with straight gas with no oil. Saw was ruined.

I am not sure how you could do that by accident, some kind of nutso passive aggressive crap, I guess. Thanks, Bud.
I am no longer friends with Bud.

The moral of the story: DO NOT lend out tools. Especially chains saws.