I've just calculated the A_Harman index. (See calculation of the A_Harman index
.) Closer to 1.000 is better. 1.000 means no VII.
PPPP 5W-30 assuming HTHSV = 3.1 cP: A_Harman index = 0.931
PPPP 5W-30 dexos 1 Gen 2 assuming HTHSV = 3.1 cP: A_Harman index = 0.975
Both are solid oils with little VII but PPPP dexos1 Gen 2 seems exceptional. Even if I assume HTHSV = 3.0 cP, I get A_Harman index = 0.944, larger than the non-dexos1-Gen-2 formulation.
dexos1 Gen 2 requires thicker base oil for protection of the timing chain in TGDI engines. (See Do you think that's thick oil? Think again?
) So, they used a thicker base oil (larger CCS) and less VII to achieve similar KV100 viscosity for the blended oil for similar protection of the bearings but greater protection of the valvetrain, timing chain, rings, and so on.