The owner's book shows the following chart:
Recommended engine oil grade: API service SE, SF, SG type or higher.
These are my suggestions:
For standard use (semi synthetic): Motul 5100 4T 10W40 or Yamalube 4T 10W50.
If you're going to race (fully synthetic): Motul 300V Factory Line 10W40, Mobil1 Racing 4T 10W40 or Castrol Power1 Racing 4T 10W40.