Same temp, same everything.  The only diff was the oil viscosity.   One of the reasons I tried this was because Bruce T mentioned that thinner oil would transfer heat better than thick oil.  Do you disagree with that? 

Well, no; but. The specific heat is the same and the flow rate around the loop is (roughly) the same.  The lower viscosity will result in more flow through the bearings and rotors (less bypassing through the pressure control valve) providing more effective cooling of the rotors.  But it has little effect on the heat rejection (other than slightly better heat transfer coefficient), so, one might expect the oil to heat up at the same rate, or a bit faster.

Unless there is something major I’m missing.

Al