I use Castrol Octaveo 10W-40 and try to change every 1,000 miles (1,600 Km's). Be sure to save an oil ring or two from the Fram Filters in case you break one using a different filter without the replacement. I've gotten about 10 oil changes on the factory oil ring so far.

If you shifting gets a little tough, notchy, noisy, etc. you should probably change your oil. Fresh oil helps the transmission shift easier and smoother and quiets it down some too.

 

This is definitely motorcycle oil .. Oil ring or O-Ring?