Do you watch yuor temperatures at all? Also 30% is not that good to run just for back yard playing. If you go to 30% you need to shim the head, richen it up and keep and eye on temps. 30% on a stock motor like the pro 15 will over heat like crazy unless you do some minor changes. You should not run other fuels other than what you broke the motor in with. 20% is the best of both. Use 20% with no more than 12% oil. 30 percent set up tha way you have it now will cook the motor.