Posted for "Christopher Zavatson" <Christopher.Zavatson@udlp.com>:
Gary,
To me those temps sound dangerously high.  I can't speak for all
Lycoming models , but redline on the O360A1A is 245F for oil inlet temp.
I imagine  the oil experiences a much greater temperature rise in these
air cooled engine since Lycoming doesn't worry about burning off
moisture until the oil remains below 140 or 160F(I forget the exact
number).  The vernatherm regulates to 180F for this reason.  I am
familiar with the higher temperature limits on oil for diesels (military
applications), but do not think it is a good idea to replace Lycoming
specifications with those of an entirely different type (water cooled)
engine.
Chris
N91CZ
360std