Re: 100:1 Mix
I haven't heard of this opti, I'll give it a try after my engine rebuild. I've been running amsoil at about 70:1 for over a year, and just a while ago at over 4500 miles I had a ring retainer pin come loose. Not sure if it was because my ratio, to much abuse, or just these 2-strokes are crappy engines. It's impossible to say. But I'm all for trying out something new.
And this'll probably elongate the oil war, but there is some truth to the "synthetic will make gaskets leak" thing.
On older engines that are nearing the end of their life anyway, it's a horrible idea to switch. Old sludgy dirty oil very well may be blocking up some potential leaks in gaskets (remember, I said old near-dead engine). Synthetic has stronger detergents in it and will clean the blocks out causing sometimes really serious leaks.
Of course, in a healthy engine, switching to synthetic shouldn't cause any trouble. If switching to synthetic actually causes an engine to leak like a sieve, that engine probably didn't have very much life left anyway or, it was in very bad need of some new gaskets.