IF you really want to know what is in the fuel ask for the MSDS sheet on the fuel (Material Safety Data Sheet). Anyone that sells fuel is required by law to have this and it will tell you the % nitro and oil in the fuel.

Something the Heli instructor said to his student Saturday was that the 15% the student was running was fine, the 30% was only for when you were trying to get that last little bit of HP out of the motor.