I use 15% Omega fuel in mine. It is an 18% oil content with both castor and synthetic. I like the idea of running some castor to coat the internal working parts. I have had no problems, and it was recommended by several others in my club. For break-in use the nitro content you plan to fly with. If you want to add oil to bring it up to 20% for break-in, fine.

More nitro runs hotter, causing more expansion of the parts, hence you can use a high nitro fuel and switch to a lower nitro as the engine gets worn, but not the oter way around. I believe this is more important in an ABC engine than in a ringed engine (such as your Saito).

It is also convenient to use the same fuel for all my plane engines as opposed to having several jugs and having to switch depending on what you're flying!! 30% nitro heli fuel is supposed to give outstanding power, but I'm just a sport flyer, and don't need it.