<<What is a decent oil temperature for take off.  The viscosity changes by
roughly 2 orders of magnitude between start up and steady state cruise.  Is
there some viscosity/temperature threshold that should be observed to
prevent damage at take off power?
Also, is there a particular reason for not mixing brands/viscosity?  I tend
to run multi weight in the winter and straight weight the rest of the
year(same brand).  There is obviously be some mixing during the change over.
Chris Zavatson>>

My opinion is that there is only a vague limit on low oil temp for takeoff
and as Craig pointed out the big risk is over-pressuring the filter if the
pressure gets too high, although aircraft oil filters are built for higher
burst than automotive filters.  I don't think oiling the engine is a problem
and if the viscosity of the oil is low enough to allow the engine to start
and run it is probably good to go by the time you taxi out and do the runup.
And I don't think there is a problem with mixing viscosities or brands.  I
also have run multi-vis during the winter and straight oil during the
summer.  If the weather transitioned before it was time to change oil I
would just start adding different oil.  Just my opinions.

Gary Casey