You kept the part that is about freezing temperatures though. 0W-20 means it is 0W at low temperatures and 20W after engine heats up. This sounds like a very bad idea since the oil pump is designed for thinner oil. So it will increase engine wear due to reduced lubrication efficiency combined with increased internal resistance.Not in my book. We don't get freezing temps and get 110+ on summer days, I drive without consideration to economy and like moving with the flow of traffic, plus I standardized with the rest of the cars in the household.
It will be “warranty denied” in Toyota’s book as well.