Engine oil temperature (operational values) are considered best when the engine oil temperature is maintained at 20 to 30*F above that of the water temperature. See the link to a discussion below.
Not to mention that you best volumetric efficiency is going to be between 195-215*F. Keeping the oil at 215* or better will allow the additives in the base oil product to do their intended job.
Here and
here are two discussions of engine oil temperature from a few years ago.