[CallMeSnake]

I have a 2012 as well. It "uses" oil just about as fast as yours. However, once I started to ride it off road and it got dirty, the culprit was revealed to be a slow leak out one of the cylinder head cover bolt grommets. Bike leaves no telltale sign of the leak in the garage. While in motion, the wind blows / sucks the oil out of the leak and then off into the air. There is almost no residual once stopped. Only the dirt sticking to the small leftover film revealed the leak.

I would agree that using 5W-40 is unlikely to cause any excessive wear on the rings. The difference between 40 and 50 viscosity just isn't that much, especially when you compare how much change there is due to engine temperature and the reduction in viscosity over the oil's life in the crankcase. Is it optimal, no, but if the oil was changed / added as needed, I wouldn't worry about it.

The fact that this started shortly after being serviced is you big clue here. Buna-N rubber has a lifespan of about 10 years before it becomes hard. An existing seal will often hold beyond that, but once disturbed it will not re-seal again. On bikes of our age, it's best to replace any seals whenever stuff is taken apart.

 

[CallMeSnake]

That much oil leaking out of a cylinder head should leave some very visible traces all the way to the rear tire I guess...

You would think, but below are the pictures of my oil leak. When the bike is clean, it's almost invisible because the oil film is so thin. Oil never gets beyond these two slightly wet areas. I think part of this is because the airflow at highway speed is causing suction at the bolt head making the leak much worse at highway speed vs. slower. The high speed air then pulls the droplets off into the airstream while in motion. The oil down lower on the head is just leftovers accumulating due to gravity.

I'm about to do the 12K service so it will be interesting to see if the oil consumption stops.

Your note to check the crank ventilation system is a good possibility too, as having excessive suction / pressure in the crankcase can cause all sorts of oiling issues.

 

[CallMeSnake]

One other note. Once the catalyst is hot and functional, it will remove a significant amount of burned oil smoke. At least until it get's poisoned from the excess hydrocarbons. If the bike smokes with a light blue color and has that burned oil smell in the exhaust just after start up, then it's burning the oil. If the smoke is white or no smoke, then it's probably not burning it. A sweet smell in the exhaust when cold is ethanol if that is used in Albania.