I was almost sold on Mobil 1 15/50. The only thing I'm concerned about now after much research is visocity shear. This is a direct quote from Mobil;
"Mobil 1 15W-50, on the other hand, will exhibit
some shear loss in motorcycle applications."
This seems to be a common trait among oils(including Castrol 5/50) with more than a 30 vicosity spread. Mobil is trying to push their motorbike formulas(mx4t 10/40) obviously.
My wish was to find a year round oil for here but thought 20/50 too heavy for cooler fall and winter and 10/40 too light for hot summer use. mx4t is not availbable locally and neither is Amsoil.
Now I'm considering Petro Canada 15/40 duron xl(blend) as another year round alternative. It is the highest rated, locally available oil in that weight according to the motor oil bible. Let the research continue!