No question, some of Mobil's stuff is still true synthetic, but the common ones (5w30 and 10w30) appear to have a Group III component in them.
Heck, even one blend of Amsoil has Group III base oils, but Amsoil openly admits it.
In the grand scheme of things, any API SM/ILSAC GF-4 formulated oils will do just fine in everyday use.