The Mobil 0w-40 made both more horsepower on a engine dyno and had less amounts in particle counts in same engine , back to back testing vs Castrol SLX 0w-30 .
Particles where not counted in that test. The difference in the power output could be explained with the standard deviation of the dyno test rig or a different atmospheric pressure. Can you exclude that in your testing?
Besides, one oil does not have to work good in all engines designs if it works well in one.