“It’s interesting, in the non-turbo version of my car, 0W-20 is recommended, while 0W-30 is the recommended weight in the turbo version.”
The oil runs at a hotter temp in the Turbo versions and gets thinner. The turbo heats the oil more than it regularly would because oil flow is how they cool the turbo bearings. Same heat issue is true in the desert southwest with extremely hot temps.
So your example says it all. Extreme heat (severe duty) conditions actually do require a little heavier oil. Such as turbo models and very hot environmental conditions. I don’t care what the manufacturer says...
The turbo heats the oil more than it regularly would because oil flow is how they cool the turbo bearings.
Another good reason not to immediately shut down a turbosupercharged engine when it has been runnin hard. Give it a few minutes at idle to let the turbine and its bearings cool down.