Without question, I've never seen so many INTELLIGENT and well informed responses to a question on this site.
No s*** guys, well damn done.
Our subject car (87 300TD) is in CA, never freezes, and he driving a cooling system POS that really struggles with the AC on in temps above 80º. Been there done that.
Shortsguy1, glean from what has been shared, you need an optimized mixture for CA that will maximize the latent heat carrying capabilities in our 100º+ heat, especially if you go inland from SLO to
PR to sip some fine pinot.