On a hot day (80F +) and going on a day trip of about 100 miles, my Sixty-5 uses several ounces of oil. No more than 60 MPH indicated.
It is broken in correctly so I'm assuming this is my bike's individual usage. And there are no leaks or oil spots on the floor when parked.
I think having a plugged breather system would force more oil past the rings because of too high crankcase pressure. The factory engineering is best not altered unless one is doing major modifications - this brings out the motorcycle gremlins big time.
Regards, Foggy