Nowhere does it say 0W30 from Mobil. Any fool knows a 0W20 can be used in place of a 5W20, our discussion is SSO 0W30 in a 5W20 application, new vehicle under warranty. I'd trust Mobil over Amsoil too.
You answered your own question a 20 grade oil is right for your car. Ask Pennzoil, bet they say a 20 grade oil too, and not mention a 30 grade. Only Amsoil suggests SSO 0W30, they have a lot invested in it and want to push it.