I am currently on this one:
I purchased Dolmar oil but they sent me the Makita branded bottle.
It seems good as some of the oil gets expelled unburnt.
Once I use up the Makita oil I'll be back to Dolmar:
I aim at 50:1 while mixing, but tend to add a bit more oil so that I should be between 40:1 and 50:1.
I am using unleaded ethanol free pump gas - EuroSuper95.
I have no idea whether the oil, fuel or the ratio I use is the best for my equipment, but other than a 9 year carbon build up on my PS-6400's exhaust port which caused some piston and piston ring scoring my OPE seems to take it very well.
FYI:
My dads Sachs-Dolmar 105, which I kinda adopted, ran on a wide range of mix ratios and oil quality - I even ran it on 15W40 engine oil added to fuel without a measuring cup!
The result?
A broken clutch weight at age 30!
The Sachs-Dolmar 105 is being mended, used clutch weight from a SD105 carcass, NOS OEM clutch drum/sprocket, new Caber piston ring, cylinder and piston cleaned up.
While I am at it I might replace the 30 years old factory original, carb kit.