Every engine is different...didn't this one come with instructions? []

As a general rule of thumb;
10% nitro for a 4 stroke engine should be fine.
I am a firm beleiver in a high Caster oil content and a long break in period with the engine running very rich for the first two tanks and then slowly leaning it out over a gallon of fuel. [8D]

However; when all else fails... read the instructions.