Elson,

Your results mirror ours with the Amsoil. If the engine is loaded to near max output the oil fails the engine rather quickly. It was better than 3W oil, but not by much. The Belray (both), Pennzoil aircooled, and a few others have proven to be far superior for engines pulling heavy loads or enduring extended flight times. Although very few of the engine pulling r/c aircraft endure the loads and stresses of "heavy" use, the lessons learned about properties and capabilities of special use oils applies across the board. Someone going with a pusher design needs to pay extremely close attention to oil qualities.

BTW, As I recall you're a professional flyer in your field as well so you get included with the "professional uav" guys