Royal Purple, Red Lion, and Amsoil are the three big ones I have seen at our field. A friend uses Red Lion on his DL-100, a few guys with big DA's and 3W's use Amsoil, and one or two use Royal Purple, I got a quart at our FX3D event this spring, and so far I like it. I try not to hound these guys too much about my future plans for a 55cc plane until the time comes, then I will begin to pick their brain.