Originally Posted By: Gokhan
Let's give the facts so that there will be some actual useful information here. Here is the recommended ingredient list for synthetic oil by ExxonMobil. Formulas will vary a little but the following is rather typical:
The difference between 0W-40 and 5W-40 is that 0W-40 starts from a much thinner base oil and uses more VII to increase KV100 to the SAE 40 level. That's the only real difference between the two grades.
Using the SPECIFIC example you've provided us with, the 0w-40 is 40% 6cSt PAO, 34.1% 4cSt PAO and 11.6% VI. This oil is significantly thinner based on MRV and HTHS than Mobil 1 0w-40 FWIW. It also has a higher NOACK. This would indicate that it (Mobil 1 0w-40) is blended using heavier bases than the product in this guide. In fact the HTHS on the actual product is the same as the 5w-40 in the chart
And of course this is just a blending guide.
Originally Posted By: Gokhan
The end result? 0W-40 benefits from lower CSS/MRV (thanks to thinner base oil) and higher VI (thanks to more VII content). However, 5W-40 benefits from lower NOACK (thanks to thicker base oil) and less oil shear (thanks to less VII content).
Also, FWIW, the old Pennzoil Platinum 5w-40 Euro had a NOACK higher than Mobil 1 0w-40 @ 11%. Pennzoil Ultra 5w-40 has a much lower NOACK @ 6.8%, and these are both Euro 5w-40's from the same manufacturer, LOL!
Originally Posted By: Gokhan
Regarding Group III vs. PAO, PCMO Group III has greater or equal VI than PAO these days, thanks to HVI Group III (Group III+) and XHVI Group III (GTL). Therefore, amount of VII content with high-quality Group III can be even less than with PAO. HDEO 5W-40 like Rotella tends to use cheaper Group III with lower VI.
It isn't just the VI, it is the amount of Pennzoil PlatinumD's needed for a Group III to meet the CCS/MRV requirements vs a PAO.
I'll borrow this picture Shannow posted before to illustrate this:
Originally Posted By: Gokhan
Last but not least, shear-stable VIIs are common these days, resulting in very little degeneration of the overall VII content over time and therefore very little oil shear
*snip*
I have been using Mobil 1 0W-40 SN recently and my engine has never run smoother. I thought TGMO 0W-20 SN was great but the Group III+/PAO/ester base oil of Mobil 1 along with a higher-quality additive package seems to have resulted in a truly premium oil.
Yes, and the amount of VII's, even in the examples you gave (11.6 vs 8.7%) is hardly what I'd call significant.
Also, you may find this graph interesting (as it specifically shows GTL):
From this Infineum presentation:
http://www.infineuminsight.com/insight/sep-2014/uncertainty-ahead-for-base-stocks
Which further demonstrates the above regarding the cold temp performance of PAO being significantly better than anything Group III/III+ regardless of the VI being the same or even lower.
This is why VI doesn't show the whole picture, because it doesn't cover true low temperature performance; it is not a replacement or even much of an indication of CCS/MRV, which is where PAO is significantly better and why a PAO-based 0w-xx can require less treat rate to meet the 0w-xx designation requirements than a Group III or III+ would to meet the 5w-xx one.
