The oil that is in the fuel is there to lubricate the engine and will flow through it and out the exhaust. It doesn't burn but will heat up as it travels through the engine and smoke when it exits the exhaust. If you don't see a smoke trail then it usually means that the engine is running too lean. On trainer planes this oil ends up on the bottom of the wings and on the tail surfaces. The dirty job after flying for the day is to wipe the oil off. Now find an Rc club and get out there and start flying (with an instructor of course!). [8D]