My 120SP may have been an exception to the norm, but it was tame before a gallon of Omega 10 was run through it and will idle indefinitely at around 1400rpm. I switched to CoolPower 10 after that 1st gallon of Omega with the same results. Judging by my experience with this engine, I'll stick with the SP engines for all of my scale projects. The only real problem I had was with the muffler vibrating loose with each run. I replaced the muffler with a coupling and a straight pipe of stainless steel and haven't had any problems since. I did beef up the firewall of my TF Corsair to handle the expected vibration.