ORIGINAL: nitro wing
I have been using 30% heli on mine,many said i was wasting my time,but I had some improvement as i was borderline on power with Funtana X100.
Try some 15 -20% that should work for you.if the motor is new,avoid prolonged lean runs and use fuel with good oil content.
Somebody told me he went through too many glow plugs on 30%, have you had any issues with that?
I've read other opinions that "the OS 120 4 stroke doesn't gain from anything over 20% nitro content"
Your 120 sounds good, I may try the 30% too
What fuel do you use?
I did buy a gallon of "Cool Power High Performance Heli 30%" but don't care to replace the glow plug excessively