Just thought of something else. The tank could cause a lean run after a while, but I think you'd really know it. When they go lean in the air, they can really scream, and you can definitely tell it. I've been scoffed at before, but I run fuel with 22% oil, 1/2 castor and 1/2 synthetic. Yes, my planes get dirty, but I've never cooked and engine, and I've had some lean runs, especially with control line using OS LA's. When the engine goes lean in CL, all you can do is fly it out and hope for the best. Luv that castor!! Glen