As a general rule, if your engine isn't using more than a quart of oil between oil changes, there is no reason to increase viscosity. By making big changes in oils (say 5w30 to 20w50), the clearances must increase to allow proper flow at cold start up. If the clearance is not already there, then it will be created. In doing so the metals are "forced" to allow the clearance by wearing. Essentially, by prematurely increasing oil viscosity you run the risk of putting wear into your engine that did not previously exist. The increased oil viscosity will actually cause wear. Always increase oil viscosity in small increments until oil consumption is under control.