It has been 90F and hotter and with AC on full and stuck in traffic idling and crawling, the temp for the car stays OK and only slightly higher than 185F, but oil pressure is dropping below one bar on these occasions. I believe the oil is now 10-40 and am thinking to go 20-50. I am in Northern CA just above San Francisco. The car does not have tappet noise and drives very nicely with what seems to me proper power. I had a 500sl in the past with the larger m119 and lower gearing. I had switched that car to 20-50 with the same thought and I think that I had an oil backup draining that caused a pressure burst in the crank case that blew into the intake manifold and blew a few air lines open. Once I had put it back together it was fine, but I did switch back to 10-40, not sure if that was the cause, but I am seeking expect advice before I proceed.
It is my understanding that being below 1 bar anytime is not really OK.
Also, I do not think that the vacuum valves to set the AC on recycle are operational as these is no change or action when the switch for recycle is pressed. I guess that those vacuum valves can fail and are hard to get to in order to service or replace.
Maybe you have a link on this procedure.