I think that it's possible that there are just variations in the spec as a result of the latest of the testing that is regularly done. It would be interesting to find copies of all of the tech specs over the years to see the variations.
I have only been able to come up with three tech sheets for Platinum. Aug, 05, Feb 08, and Apr 09. All list 5W-30 SM GF-4 oil. The tests with the most variations are
Test Aug 05 Feb 08 Apr 09
Pour point°C -45 -45 -39
MRV °C 6,600(-35) 15,700(-35) 14,800(-35)
CCS °C 4,410(-30) 5,200(-35) 5,150(-35)
Nowack % 12.5 11.6 12.5
I know that there were sheets out between 05 and 08 and I seem to recall that at least one (07 I think) also listed the pour point at -39 but can not recall the Nowack.
Does anyone have all of the Tech sheets for Pennzoil Platinum?