My only concern with colder oil temps is not getting al the moisture out of them through evaporation. I like to have mine 180 or above to make that happen.
Are you sure the thermostats are ok? My car will sit just below the white line for about 90C/194F. At most it's 1 needle width below that no matter the outside temp is. It seems to me that, if the thermostats are working right, the engine thermostat should be partially open to hold temp in the engine. This gives you an idea of where on the gauge it sits, from another Pelican post.
