Amsoil MCF, MCV, and Mobil 1 Racing 4T and V-Twin consistently turn in the best results. When it was included, HP4 did OK, overall. It did fall out of grade during the viscosity shear test I consider so important, but it took longer than most by far. Motul oils do well, as do the Torco and Spectro MC oils. Just be sure you don't use the MB version of HP4 (you knew that already).