I am the source for the Red Line Viscosity-Index-Improver info, and Red Line is my source. Dave Granquist told me in writing that the 5W-40 is the only RL oil that uses any VIIs.
I'll be using RL 10W-40 in our very-hot summers and 5W-40 in nonsummers, changing each 6 months at what will be c. 11,000 miles. (Porsche recommends 20,000-mile intervals.)