I have been watching this thread and hoping to see definitive answers.
I have seen first hand the adverse results of mixing coolants. Gelling, crystallization, and separation.
Through the years there are also reports of adverse interactions with specific gasket and seal materials, and even metals and plastics in the cooling systems, when using the wrong (not specified) coolant.
The "old standard" green antifreeze is a silicate and phosphate product.
Newer products are OAT, Organic Acid Technology and, HOAT, Hybrid Organic Acid Technology.
The coolant in our Giulias (information provided by MacGeek) is Petronas Paraflu UP, a "monoethylene glycol base organic acid technology" (OAT) swill.
On the same MacGeek spec sheet it lists: Chrysler MS-90032 and Fiat 9.55523 specifications. If you go to the Petronas site, the Paraflu UP page gives the same Fiat compatibility numbers, but a different Chrysler MS-12106 number.
I hope that I don't need to add coolant until this is cleared-up.