Why motor oils are becoming thinner and thinner and why motor oil may no longer contain any oil at some point
www.liqui-moly.com
According to this article, the reason for using increasingly less viscous oils is only that it costs less for the lubrication pump to move it and this reduces fuel consumption. It's not because it lubricates better.
I will continue using 5w40 for my THP, the engine runs smoother and quieter than 0W30 and consumes less oil.
Currently, for the most recent engines, the recommended oil is usually 0w20 !