Posted for "John Schroeder" <jschroeder@perigee.net>:

 Douglas -
 
 We have the same situation on our IO-550N in an ES. This winter, we noted the
temps in the lower 160's and with the oil cooler door fully closed they
finally got up to about 185-190. 190 is about a minimum. We also run 2300-2400
and LOP at 8000'.
 
 As I understand the reason for concern about oil temps being on the low side,
this is barely high enough, to cause the water in the oil system to vaporize.
Water condensing in the oil is a source of internal corrosion, and corrosion
has a considerable effect on things like getting to TBO.
 
 One thing to check is your temp sensor in a hot oil bath. It may be faulty.
How are the temps in summer?
 
 Cheers,
 
 John