Hey Steve:
The reason most of us an
oil cooler is that the cars are replicas. The originals had
oil coolers!
I get around the concerns you have by using 5W-30
synthetic year round and blocking the cooler whenever the ambient is below 70 degrees F.
The fact is we don't need the big blocks, we don't need the Webers, we don't need the knock-offs, and we don't need the
oil cooler, but if we didn't have that stuff it wouldn't be much fun.
Bob