I would also add a thermostat into the mix. IIRC, Permacool sells them. That way, without the coolant to help warm the fluid in the winter, you wont overcool and never reach operating temps. The one that they have keeps 5% or so of the coolant passing through the cooler at all times to eliminate cold oil shock when the thermostat opens. I believe they said that it was a 190 degree thermostat.
