Seems logical (and obvious) that a "thicker" oil would leave a denser film less prone to wiping removal, the same way a car might hydroplane on very wet mud at 30 mph while it might not with dirty rain water at the same speed. And if the remaining wiped oil film is thicker, it's more effective at preventing metal parts from contacting, thereby increasing time required to obtain the same amount of wear. But as others have noted, the various anti-wear/film strength/friction modifying additives complicate such simple logic.