[Peakster]

The 1.0L engine has no problem staying warm and generating cabin heat at steady highway speeds. The problem is when driving in stop/go traffic.

One particularly cold night (-30*C) I drove to the closest movie store about 4 miles away, all surface streets with speed limits between 30-45 mph. I never shifted higher than 3rd gear, even on the 45-mph stretch (in that I was doing 50) and the temperature gauge was almost in the middle by the time I arrived. Not quite fully warmed up though. I decided to leave the car idling while I looked for movies to keep it warm. 15 minutes later I came back and the temperature gauge was right back on the "C" again!

That tells me that the radiator fluid is swishing around at all times, regardless of temperature. Honestly, if radiators didn't circulate liquid until a hot temperature is met, what would be the purpose of blocking off a radiator like so many do in the winter?