I accidentally overfilled the crankcase by an ounce or so, and it was just barely over the Full mark. Last time I checked it, it was dead on the Full mark. I've probably used it for 10-15 hours over the past year.
Past lawnmower that was neglected and never had it's oil changed until the day it ran dry and seized. I refilled it with Mystick SAE 30 and it would use some about every time I cut grass. I put in Amsoil XL 5w30 and it had far less oil consumption, which I figured could be because it cleaned up some gunk inside and the dirty oil would not seal well around the piston area. I then put in the Amsoil 0w-40 and it never used oil again.