Jim Macklin wrote

But if you are
flying a multiengine aircraft in cold weather and shut an
engine down in training including feathering, the oil may
congeal to the point the prop won't unfeather. So ME CFI be
careful what and where you practice.

That is true of course unless you happen to be flying a big
turboprop that uses something similiar to hydraulic oil for
its prop control mechanism. We routinely shutdown (feathered)
numbers 1 and 4 for endurance purposes.

Bob Moore Allison T-56 operator