This sounds more like a Stihl problem than an oil problem. I use 100:1
synthetic in my Stihl chainsaw. After 20 years and cutting 1-2 cords/year it
runs and starts great.

Chas Hurst

100:1 synthetic is fine. it's the cheap outboard crap that gets
people into trouble. outboards are water cooled, lawn wquipment is air
cooled and runs hotter.
quality oil is fine, crappy i only want to spend 50 cents oil is
not.
Chip