Bror - I don't think that Pennzoil or anyone else sells a "pure" Group II plus oil. If you wade through the various Chevron links and associated publications, they indicate that other producers make a low viscosity Group II plus base oil similar to their 5R. No other Group II plus base stocks are indicated.
The best conventional oils are blends of all hydrocracked Group II base stocks. It is the absence of Group I base oils in the blend that provides the greatest improvement in oil stability. Even thought a Group II base can contain as much as 10% unsaturated hydrocarbons, typical hydrocracked Group II base oils contain dispersant and anti-wear compounds. This, plus the need for less VI improver allows for the competitive prices. Good chemistry and efficient manufacturing procedures keeps the costs low.
The best conventional oils are blends of all hydrocracked Group II base stocks. It is the absence of Group I base oils in the blend that provides the greatest improvement in oil stability. Even thought a Group II base can contain as much as 10% unsaturated hydrocarbons, typical hydrocracked Group II base oils contain dispersant and anti-wear compounds. This, plus the need for less VI improver allows for the competitive prices. Good chemistry and efficient manufacturing procedures keeps the costs low.