This is current PAO SpectraSyn4 from XOM.
Pour Point -66
Other than at the South Pole in winter XHVI, Viscom, and PAO are comparable other the VI for PAO is a great than 10% less than XHVI. Nearly 20 year old XHVI looks to be a better virgin performer than current XOM "synthetic" base stocks.
I have used a goodly amount of both Shell XHVI & HVI in my time.
Back in the day it was something really special. It predates my time in lubricants but in the late 80's, I'd sit in on discussions with Shell Geelong (90% of which I didn't understand!) and it was very clear then that they were extremely proud of 'their baby'.
Today however, the Shell XHVI route to Group III synthetic base oil really doesn't make economic sense. The XHVI process catalytically hydrogenates 'slack wax'. The primary source of 'slack wax' is traditional Solvent Extraction / MEK Dewaxing (or Propane Dewaxing in the case of heavy Bright Stock) for Group I base oils. Since the API & ILSAC introduced tight limits on the sulphur content of engine oils, lots of traditional Group I base oil refineries have been permanently shut down, choking off the supply of slack wax feed.
It's far simpler & cheaper to just catalytically hydrogenate & catalytically dewax Vacuum Gas Oil directly especially if you have access to VGO derived from naturally very waxy crude oils (like Petronas in Malaysia). I don't know, but I'd hazard a guess that today, 95% of the Group III you find in engine oil comes via the VGO route with the 5% balance coming from GTL or the slack wax route.