Hey Guys, I've got a Saito 62 four stroke turning a 12x6 prop and I'm using Magnum 15% with a synthetic/castor mix. I broke the engine in with this stuff and have been using it with no problems. The manual says not to turn more then 11,500 RPM so I've got it turning at 10,200 max RPM on the ground. The engine runs fine in the air and I haven't had any trouble but I did have to adjust the valves finally. Anyway, after some flights I've noticed a black oily residue on the front of the plane and wing. I can't tell if this is good or bad and the fuel coming out the blow by tube underneath looks fine with no color at all. While I'm flying most of the time I fly 3/4 throttle and the engine doesn't seem over heated at all. Is this black oily residue normal?