Hot off the phone, current HTHS viscosities for most Valvoline PCMOs:
5w20 AllClimate, Durablend, and Synpower: all 2.6
5w30 AllClimate, Durablend, and Synpower: all 3.0
5w30 Maxlife: 3.2
5w30 Maxlife Synthetic: 3.5
10w30 AllClimate, Durablend, and Synpower: all 3.0
10w30 Maxlife: 3.3
10w30 Maxlife Synthetic: 3.6
10w40 AllClimate, Durablend, and Maxlife: all 3.5
Given the importance of a robust HTHS viscosity, it is clear that Maxlife is the King of Valvoline, except in 10w40 I would put Durablend right alongside Maxlife. And the Maxlife Synthetic leaves Synpower in the dust.