If you dig around on the XOM web site and look at their reports on the wax isomerization unit at Fawley, you can see why they have gone to all Group III on their conventional PCMOs (at least in the US). Now that Fawley is in full swing XOM can produce Visom base oil (formerly known as ExxSyn) at a lower price than all hydroprocessed Group II and Group II+. Visom is a wax isomerate base oil (like Shell's XHVI) that has a VI of >140, extremely low pour point, and exceptional purity. Unlike hydrocracked Group III base oils, which still have some napthenic compounds, wax isomerates are almost 100% iso-parafins making them the only Group III that can be used to blend 0wXX oils without the use of some PAO.
What this boils down to is that the new Mobil Clean 5000 oil is probably better than 99% of the other Group III "synthetics" being sold at 3x the price.
What this boils down to is that the new Mobil Clean 5000 oil is probably better than 99% of the other Group III "synthetics" being sold at 3x the price.