Oil feels very thin despite being 10W-50

In turbocharged race cars, many years ago before the commonly available synthetics, we found that the oil quality goes beyond the viscosity label. A 20W-50 might feel wonderful between the fingers, but result in connecting rod bearing issues under 33 pounds (2+ Bar) boost. This was due to inadequate HTHS coupled with poor temperature control, not it's initial viscosity. Today, we can clearly use a high quality 5W-30 synthetic that is water thin between the fingers but has an HTHS of 3.5, and will, if temperatures are well managed, protect that same engine with 33 pounds boost.

The guys that run the Ford Ecoboost engines with that much boost make huge HP and often choose an oil with an HTHS of 3.8.