[s-cars] Coolant temperature questions

[Kevin Day]

Here's a puzzle: why does the engine temp as reported by the CC drop by
5 or 6 degrees in 20 seconds when I turn the heater off?

I saw similar temps on my commute this morning (20 miles of highway) as
I did before I started noticing a drop a few weeks ago -- 88C steady at
speed, peaking to 92 stopped.  But then I noticed that if I turned the
heat off, the temps dropped rapidly.  This seems like a small time
constant for anything to cool off -- any ideas?

It's repeatable -- if I turn the heater on again, the temp rises to 92,
off again it drops to 87 rapidly.

-Kevin