The engine masters video reinforce’s that the oil which makes the most power is the thinnest oil that has the best ring seal. In the case of the engine masters video with the stock 454 the 20w50 simply had better ring seal than the 5w30. A lot different than ultra thin rings on gas port pistons. You don’t always know what the engine wants until you try something different.
Best ring seal probably shouldn’t be in the most important category for engine oil in a street car.
