During the warm months, the Series seems to run at a pretty constant temp, goes up a bit on stop and go.

Since the temps have been in the 40's and below, it barely breaks 120 degrees.  This is not quite enough to run the cabin heater very well, and in these temps, I wonder about the viscosity of the oil overall.

Should I muff the radiator grill?  If so, how?  Any ideas?

Ben,

In my experience, I ran a radiator muff on my Series IIa and I changed the thermostat to a 190 degree unit so the block would heat up faster. Never gave me any problems at all.

Radiator Muff

Dan

I put on a radiator muff from Rovers North in the winter (if you can call it that) here on Vashon Island, WA. Really improves the engine temp.