>
> Thanks David for the detailed explanation.
>

You're welcome. :)

I find that even the inexpensive IR guns are very useful.
>

Absolutely.  And surface temperature probes have their own problems.  So
much easier if you can bury the sensor in a mass of whta you're measuring.

> Agree, shiny objects don't work. Most everything in my West engine
> compartment is matte, or dirty/dusty. Wouldn't that make emissivity
> reasonably close to a black body emitter?
>

It certainly helps.  But if in doubt, bring out the tape/paint/whatever.

Yrs,
d