Personally, I wouldn't trust either one. M1 is supposedly fully synthetic, but they don't commit to anything on the label. I'd bet it uses mineral based stock since they won't say otherwise in writing. Castrol admits that Syntec is made from mineral stock, and they say that Edge actually uses POA, but they won't say how much... therefore, I still don't trust them. That said, both oils are probably good, but I would be careful of claims that you can go X number of miles between changes.