TO, I now use a 2 stoke Rotax, used to use an HKS 4 stroke. Mogas is apparently better for these engines (inc. 912) (runs cleaner, less deposit buildups), and I use it for preference, but when landing out I use 100LL just because it's less grief to get hold of. Never had a problem with either, and no problems that I have heard of in rotating usage of both. Just for the sake of belt and braces, I always get mogas from high-turnover service stations - I might be wrong, but the constant pump flow probably helps avoid dirty nozzle internals, storage debris and the like.
Fred's unbranded petrol from the back of the donga where he filled up a car last week if he's lucky might not be the best thing to bet your airframe on.