The information I read contended that the 0w oils, due to having to use different base stocks to reach the 0w rating, would over time shear down less than the 5w and 10w competition. E.g. after 3000 miles of use, at full operating temp they would still be acting like a 0w30 or 0w20, whereas a 10w30 might start acting like a 10w25 or a 5w20 might start acting like a 5w15.
In the case of the M1 afe 0w20 vs regular M1 5w20, the argument was similar to the difference between US and German Castrol. Better base stocks in the Ow making it perform better even at the 20 end of the spectrum. Regular US spec M1 doesn't seem to be anyone's favorite but the are seems to be well liked, similar to the German/euro spec stuff.
Now. This may have come out before it was revealed that some manufacturers have successfully made 0w oils from the "lower quality" base stocks as mentioned. Or itay be specific to certain lines or brands.
Remember, oil companies are under no obligation to use exactly the same stock mixture or even quality from weight to weight in the same line. They're all about the bottom line, and if they can meet their requirements with a less expensive blend, they will, as 99% of consumers don't know our care to know the difference.
The PP 0w20 has a stellar NOACK score and middle of the road viscosity index. This should indicate a lower level of viscosity modifiers than say the Toyota OEM oil. Per the SOPUS paper on deposits, this should be helpful. Hence my choice to use it.
Thanks for helping to clarify my three sentence generalization.
Cheers
Nathan