re: Is 0w20 really what is best for our vehicles?

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The difference is at engine startup where 0w20 is going to be less viscous and will lubricate better when the engine is cold.

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It makes zero difference unless you are far below freezing temps and even then it's a pretty small difference. I run full synthetic 10W30 oil year round down here even though the oil caps say 5W20 and 5W30, I switched to synthetic 5W30 during the winter in Pennsylvania. There's a reason OEM's only state these CAFE oils provide "adequate" protection here, and in the exact same engines elsewhere they run higher viscosity oils. If you installed a mechanical oil pressure gauge you'd see for youself there is little difference in cold-start pressure between a 0W, 5W, or 10W. Also, more vehicles use variable oil pumps where pressure is partially managed with throttle input, all to get a few more tenths of a mpg for CAFE and zero benefit for engine longevity.