0w20 vs 5w20 Pennzoil in my Dodge Challenger V6

A local car guru says that using Pennzoil Platinum 0w20 might be "better" than Pennzoil Platinum 5w20 because it has a higher viscosity Index of 182 vs 167 VI of the 5w20.
Is the higher VI better for California driving?
A higher VI just means it has less viscosity change between 40C and 100C. The VI calculation uses the oil's kinematic viscosity (in cSt) at those two temperatures. A 0W should typically be thinner at 40C (and more so as temps fall farther below 40C) than a 5W, so that too would help give the 0W-20 a higher VI compared to a 5W-20 with similar formulaton. The higher the VI, the flatter the viscosity vs temperature curve between 40C and 100C.

The VIIs are not the only thing that determines the VI. The base oil starts with it's own VI before any VIIs are added.

The one with the highest HTHS viscosity is the "better" one.
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