Originally Posted by TboneZX3
From my understanding, it is still speculation that Shell is using GTL stock in Ultra. That speculation is based upon the low published NOAK in the SN data sheet. Shell has announced the Pearl GTL plant in Qatar is now up to full capacity, but I have yet to see any proof that Ultra is derived from those stocks.
True, but Shell did report its first delivery to the US of GTL base stocks from Qatar anout the time the new SN formulation of Ultra was introduced. Shell has said a primary use of GTL base stocks is in premium lubricants and Ultra is their top-of-the-line lubricant in North America. Plus the low Noack, of course, which is a natural consequence of GTL base stocks.
Shell, Mobil, etc. don't typically divulge much information about the composition of their oils so we're unlikely to get a definitive answer. But it sure looks like GTL to me.