So far those fears have not come to fruition.
The damage done to timing chains in Ford engines after Ford switched their oil viscosity recommendation from 5W-30 to 5W-20 took over a decade to materialize. Ford has switched it's recommendations back to 5W-30 for many of it's engines.
The switch to ultra thin oils (0W-16 and someday 0W-8) won't have problems materialize during the typical 60,000 mile warranty period.
Those issues are likely to materialize after 100k miles with high oil consumption and worn out engines.
In my opinion, the Europeans got it right when they focus on HTHS (High Temperature/High Shear) as an important oil protection property.
Certain parts of an engine get "extrememly hot" and also the oil experiences high shear during higher RPM's.
20 weight oil is typically at a HTHS of 2.6 when the oil is new, but it will sheer down to lower HTHS numbers after 4k to 5k miles.
Any HTHS below 2.6 has been shown to cause exponential engine wear.
Just google it, see the chart on HTHS below 2.6 and engine wear exponentially increasing.
I'm not looking to start a debate. My focus in this discussion is on long term engine longevity, as I typically keep vehicles for more than 10 years. The greatest freedom all of us have is to use the oil which protects their engine the best, which is not necessarily what the Cafe fine fearing Automaker's owner's manual recommends.
