Dr. T, I just contacted Castrol and asked for a new tech data sheet for the 0W-30, 5W-30, and 10W-30 Syntec. If they send me a new tech data sheet I will forward you a copy of the PDF file. In the past Castrol has had all grades of Syntec on one sheet (0W-30 through 20W-50).
Now that you mention it the Castrol Syntec 5W-50 and Quaker State Full Synthetic Motor Oil 5W-50 do look very similar. The higher flash point and lower pour point of the Syntec is still so close to the numbers for the Quaker State synthetic oil that in the real world the difference probably means nothing. I think it is unlikely that the Quaker State synthetic oil has a very high amount of PAO or Ester since it does not have a very low pour point. The very high viscosity index of 193 for the Qaker State synthetic oil would seem to indicate to me that it may not be as shear stable as the Syntec or for that mater most other synthetic motor oils avilable. The V.I. of Castrol Syntec 5W-50 is 175 and the V.I. of Mobil 1 0W-40 is 187 and many people have critisized these oils for not being shear stable. Still both Castrol Syntec 5W-50 and Mobil 1 0W-40 have both given good wear numbers. I have never seen any UOA's on Quaker State synthetic oils so I can only speculate as to how good they may be.
[ October 17, 2003, 12:02 AM: Message edited by: Sin City ]