Hi Terry,

infused are manly produced using extra virgin olive oil. It's
particularly important to use extra virgin because with the herbs you
introduce enzymes and chlorophyl that will increase the rate of
chemical degradation of the oil. Extra virgin with it's content of
polyphenols can some how minimise this effect, but the expiration date
should be set only to six months because your still increasing the oils
rate rancydification.
Infused oil is produced just by putting in the same bottle the herb and
the oil and waiting (or whooping) the flavours get in the oil. Only
dried herbs should be used, because if you use fresh ones there is a
risk of foodborne botulism, since ultra-pasteurization isn't an option.

In my personal opinion infused oils aren't of any practical use in the
kitchen, they're just about marketing the oil. They don't get that
much flavoured and do to they're low stability they rapidly get a
rancid flavour.
If you want to cook with herb flavoured oils, these should be made
immediately before use, by infusing the herbs and the oil in a
bain-marie for 10 to 15 min.

Regards,

João