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Bob;
I’m sure that different engine/oil cooler designs affect how much the cold
air affects the cooler.  +10F air at standard density isn’t really that cold
for a lot of North America.  I know that in my C182, without the baffle in
place, on several occasions the oil congealed to the point that pressure
relief bypassed the cooler, engine oil temperature went high enough that my
prop governor stopped functioning, and I was concerned enough about the oil
temperature that I slowed the plane up to nearly ‘slow flight’ conditions.
After a period of 15-20 minutes, the heat transfer from the engine/cooler
mounting warmed up the congealed oil in the cooler enough that it started to
flow again and restored my prop governor operation and oil temperatures.
The engine in the C182 was a 470 Continental, and not sure but assume there
was a temperature sensing flow control also.  The point is that at low
temperatures, the minimum flow rate as permitted by a thermostatic device
may not be high enough to keep the engine oil from congealing in the oil
cooler unless there is some restriction to the amount of cold air passing
through the coils.

Regarding temperatures, I often started out with an ‘on the ground air
density temperature of –25 to –30F.  That’s why the need for baffles is not
geographically universal.  I’m sure that north and west of where Scott
lives, they can also experience similar conditions.

Gary

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