Oil and Lubrication
I am reading the owner's manual and it promotes the Yamalube brand (free advertising for Yamaha). The SAE viscosity grades that it recommends are:
10W-50
10W-40
15W-40
20W-40
20W-50
I have found this resource which is very useful:
Maintenance Schedule
Here, it mentions:
Yamalube 10W-40 or...