Stihl saws from 79 on (not much experience before that point with Stihl saws, we used homelite in the back 40), seem to run on 25-1 if using generic oil, and 50-1 with Stihl oil. I have a 090, and used to have something like an 010 from that period, plus a friend had just about everything they made. I have an 026 at the moment, but it is probably almost 20 years old, they seem to have changed the numbering on those. I put minor amounts of seafoam in each fill, like a cap's worth from the SF bottle.
I use Youtube for most of this kind of instruction these days. Chainsaw setting seems to have gotten more scientific with the availability of aps for your phone that let you work from known rpms for the various setting. I don't have a phone, so no aps for me, but it was interesting to see what people were doing.