Your question implies that there is only one diphthong in classical Latin. There are actually six:
The Latin dipthong ae is pronounced "-ay" as in "say". Thus, Phaedo is pronounced "Fay-doh."
PRY.
ameesisiimus
You would say milly- tes to pronounce milites.
dipthong
a big dipthong
The Latin word "pleni" is pronounced as "PLEH-nee".
viridis
communicare
pull kair
The Latin word for wolf is lupus, pronounced loo puss
in classical latin, it is pronounce spayss In ecclesiastical latin it is pronounced spayz