Originally Posted by edyvw
This is correct, but only if base stock is same.
Mobil1 ESP Formula 5W30 had much lower Noack than any 5W20 product from same company.
But then, products had different applications.
Yes, M1 ESP 5W-30 is an entirely different oil, with HTHS ⥠3.5 cP. The same goes for API CK-4 5W-30 HDEOs. Their base oils are nice and thick along with their strong HTHS.