I do not have e-free gas available locally. I run AMSOIL Saber at 40:1 in everything and it seems to stay good for long periods of time and when a builder ripped one of my saws apart, he said the parts were well oiled. It also burns clean. It even seem to prevent the inferior bearings in Asian clone saws from failing, and one of my Asian 660s dynoed at 8.6 Hp.
I currently have 17 running saws, so some of them don't get used for long periods of time. (Different saws for different stuff). I like the 660s for milling and I have 5 of them, but sometimes I don't mill for long periods of time.
I would never say it is the best, but it works real darn well! Much, much better than the Stihl oil at 50:1 (and if you run that at 40:1 it is dirty).
When something works for me, I don't change it.