Here's the setup actually running.
One thing that I discovered is that the copper coils around
the grease filter are not up to temperature until several
miles after the car's temperature gauge shows 190 degrees.
Then I'm sure it takes some time for the grease filter itself
to heat up. In fact, the copper coils never topped 160, and
when running below 2000rpm, the coil temperature drops to
as low as 110 (ambient temperature was about 48). This
surprised me... I expected those coils to reach about 190
at about the same time the car's temperature gauge did. I'm
afraid this is showing me that I've been switching to VO
before it is heated up well enough and that the grease
filter *never does* heat up to an operating temperature of 170
or more.
I'm going to try putting the sensor on the injector pump
next. Since that's mounted on the engine, I'm guessing that
it will be warmed up more quickly than my external grease
filter. If the injector pump is warmed up, I think that will
suffice (as long as the grease isn't stone cold), because the
return line T's back into the incoming fuel line. This means
that most of the fuel that gets injected has gone around
that loop probably several times -- becoming warmer with
every pass.
I'll post my results when I have them.