This is the way this works...
From a base oil point of view, Di-esters usually give you the lowest Noack followed by PAO, followed by GTL, followed by normal Group IIIs. These are followed by Group I & II base oils, which can vary a lot depending on source, but should be treated as roughly equivalent and the worst.
VII polymer type & SSI will impact on Noack. For a given viscometric balance, a 5W20 based on Hydrogenated Styrene-Diene (HSD) VII will have a lower Noack than one based on cheaper, commoner Olefin Copolymer (OCP) VII. Likewise, an oil based on high SSI (ie more shearable) VII will give you a lower Noack than the same VII with a lower SSI (typically used in European oils).
Oils that contain a lot of DI additive will have a higher Noack than ones that contain less DI. Typically, European PCMOs (which are formulated to handle both gasoline & diesel) have higher DI treats and directional have higher Noacks than say US gasoline-only PCMOs.
Finally (and this is a biggie so pay attention!) whether a 5W20 is blended viscometrically 'tight' or 'slack' has a HUGE impact on its Noack. At the extreme, a tight 5W20 will have a KV100 of 6.91 cst and a CCS-30 of 6,599 cP. At the other end of the scale, a 'slack' 5W20 might have a KV100 of 9.29 cst and a CCS-30 of say 3,301 cP (if it goes much lower, it risks becoming a 0W20). Both of these oils are valid 5W20s yet the latter slack oil will have a much higher Noack than the tight oil. US ILSAC oils tend to be slacker than the equivalent API oil. Euro oils tend to be tight in general.
So in summary, for the lowest practical Noack, you want a 5W20 blended with a mix of Di-ester & PAO, formulated with a high SSI HSD VII and a low DI treat Add Pack (say SL) that's blended tight by someone who understands how to do these things properly (like me!). Failing that, look for 5W20 oils from Redline or Amsoil.
Having said all that, I personally wouldn't obsess about using the absolutely lowest Noack 5W20 oil I could get my hands on. My primary beef about Noack is that in the US, you can still find oils with close to the 15% Noack limit. This is TOO HIGH!! A more sensible limit is 13% max as this forces out the most volatile light base oils which do so much damage to oil control rings. A better limit, if you intend to keep your car going for decades might be 10% max. Beyond 10% then benefits of lower Noack I'd judge to be marginal and probably not worth the on-cost. The way to philosophically rationalise this is that Noack-wise, life is not about coming first; it's about not coming last...
From a base oil point of view, Di-esters usually give you the lowest Noack followed by PAO, followed by GTL, followed by normal Group IIIs. These are followed by Group I & II base oils, which can vary a lot depending on source, but should be treated as roughly equivalent and the worst.
VII polymer type & SSI will impact on Noack. For a given viscometric balance, a 5W20 based on Hydrogenated Styrene-Diene (HSD) VII will have a lower Noack than one based on cheaper, commoner Olefin Copolymer (OCP) VII. Likewise, an oil based on high SSI (ie more shearable) VII will give you a lower Noack than the same VII with a lower SSI (typically used in European oils).
Oils that contain a lot of DI additive will have a higher Noack than ones that contain less DI. Typically, European PCMOs (which are formulated to handle both gasoline & diesel) have higher DI treats and directional have higher Noacks than say US gasoline-only PCMOs.
Finally (and this is a biggie so pay attention!) whether a 5W20 is blended viscometrically 'tight' or 'slack' has a HUGE impact on its Noack. At the extreme, a tight 5W20 will have a KV100 of 6.91 cst and a CCS-30 of 6,599 cP. At the other end of the scale, a 'slack' 5W20 might have a KV100 of 9.29 cst and a CCS-30 of say 3,301 cP (if it goes much lower, it risks becoming a 0W20). Both of these oils are valid 5W20s yet the latter slack oil will have a much higher Noack than the tight oil. US ILSAC oils tend to be slacker than the equivalent API oil. Euro oils tend to be tight in general.
So in summary, for the lowest practical Noack, you want a 5W20 blended with a mix of Di-ester & PAO, formulated with a high SSI HSD VII and a low DI treat Add Pack (say SL) that's blended tight by someone who understands how to do these things properly (like me!). Failing that, look for 5W20 oils from Redline or Amsoil.
Having said all that, I personally wouldn't obsess about using the absolutely lowest Noack 5W20 oil I could get my hands on. My primary beef about Noack is that in the US, you can still find oils with close to the 15% Noack limit. This is TOO HIGH!! A more sensible limit is 13% max as this forces out the most volatile light base oils which do so much damage to oil control rings. A better limit, if you intend to keep your car going for decades might be 10% max. Beyond 10% then benefits of lower Noack I'd judge to be marginal and probably not worth the on-cost. The way to philosophically rationalise this is that Noack-wise, life is not about coming first; it's about not coming last...
