Back in college at the beginning of a physics lab I was taking, I observed Dr. Onley, a pure egg head noted for his work in computer design and his teaching assistant in a heated argument over the wave length of the laser we were going to use in the experiment of the day. After about ten minutes or so of this wondrous academic discourse, I saw the laser had a tag on it with the wavelength printed on it for the world to see. What does that have to do with this discussion??? On this and several other threads I keep seeing the question of warranty come up over and over. CALL YAMAHA CUSTOMER SERVICE!!!. I did, and they will tell you 10W40, 15W50, et al, WILL NOT void the warranty. I've got the date I called and the name of the guy I talked to. Plus they logged the call to the VIN of my bike. So keep on debating whether or not the sun comes up in the east, it's just another total waste of bandwidth like just about everything associated with these oil threads.