I think you hit the nail on the head rctrax. Blackie, you must have just the right combination of where your exhaust is pointed along with the aerodynamics of your planes.

I use mostly OS 70 Surpass, OS 91 Surpass, and YS 91AC.

For 2 strokes, I use mostly 40-50 sizes.

Like rctrax says, most of the time I don't even clean my 4 stroke planes, whereas my 2 strokes (and I'm not running them rich) will have a stream of thick oil, 2 or 3" wide, running the entire length of the plane.

With my YS91AC, blowing smoke between the bipe's wings, it still doesn't leave nearly as much oil as the 2 strokes do.