Originally Posted by Gokhan
Originally Posted by StevieC
Out of these two oils, why wouldn't you use the 5w20 over the 0w20 when the properties are almost identical but the Noack is far superior... Should consideration be given to the V.I. difference?
Your thoughts?
The basic answer is very simple but no one has given it so far. I'll answer it:
The difference is in the CCS -- 0W-20 measured at -35C and 5W-20 measured at -30C, which means that 0W-20 uses a thinner base oil. This results in a lower NOACK for 0W-20. It also results in more viscosity-index improver (VII) for 0W-20 so that the KV100 and HTHSV for the finished viscosities will be in the correct range for an xW-20 grade.
Now, the complicated answer:
One thing we cannot tell from the numbers is the base-oil type. For example, M1 0W-20 uses a lot more PAO than M1 5W-20 according to the MSDS. In fact, M1 EP 0W-20 is mostly PAO. So, in the case of M1, do you care for more PAO or less VII?
Most importantly, is there any good science that more VII in 0W-20 will result in less wear protection for it than for 5W-20? One can argue that more VII is actually better because it results in a higher viscosity index (VI), which means that a 0w-20 will thin less than a 5W-20 if the temperature rises to, say, 170 C (which is well above the 150 C the HTHSV is measured) in extreme operating conditions. I would think more VII would help you in that case by keeping the oil thick.
Yes, there is this scientific paper by Nissan/SAE that claims that a thicker base oil may be better for timing-chain wear. However, does it really make a difference when a good antiwear/extreme pressure/friction modifier (AW/EP/FM) package is used?
Of course, you also get better fuel economy with 0W-20 than with 5W-20, especially in warm-up situations.
Lastly, NOACK. The only thing that it really affects is the oil consumption but if you don't have oil consumption or your oil consumption is unrelated to NOACK, it's a moot issue. We've already debunked the myth that lower NOACK results in less PCV mist and/or less intake-valve deposits.
For Mobil 1 xW-20 varieties, I would pick Mobil 1 Extended Protection (M1 EP) 0W-20 because it's a PAO-based oil unlike any other Mobil 1 variety except the Mobil 1 Annual Protection 0W-20 and Mobil 1 0W-16.
For Amsoil Signature Series (SS), I would probably still pick the SS 0W-20, even though chances are good that both the SS 0W-20 and SS 5W-20 are PAO. A little more VII? Perhaps it's actually better. It's funny that in the past Amsoil had the lowest four-ball-wear number for SS 0W-20 among all of their oils, and now, they put the same number for the entire SS series.
And a 10K OCI wouldn't be in the cards either.
![[Linked Image]](https://www.bobistheoilguy.com/forums/attachments/usergals/2018/08/full-22880-30504-noack.png "[Linked Image]")
