"Does Mobil 1 claim 15 K miles ONLY with their Mobil 1 oil filter I wonder?"
According to the Mobil website, no, as there are no special filter requirements, but the Mobil filter is recommended (of course).
"Does this apply to rear end differentials and automatic transmision fluids?"
As long as the equipment is mechanically sound, then you're safe to use Amsoil or Redline for the GM service intervals (if not longer).
According to the Mobil website, no, as there are no special filter requirements, but the Mobil filter is recommended (of course).
"Does this apply to rear end differentials and automatic transmision fluids?"
As long as the equipment is mechanically sound, then you're safe to use Amsoil or Redline for the GM service intervals (if not longer).