My grandfather used to strain used oil through a cheese cloth “to catch any sh*t” and that’s all we used for bar oil. I don’t remember any adverse effects or oiler problems. We also ran 2 stroke oil of any flavour. outboard, snowmobile, whatever was on sale, again no issues that I remember. Cutting 50-60 cord a year, trees for lumber, etc.
Now that’s it’s my gig I run amsoil saber and bar oil. Buy both by the case load and the price is reasonable enough I don’t care. When I look at profit margins bar oil and amsoil aren’t going to put me under.