Honda 2006 RC51 Owner's Manual page 98

Oil Recommendation
API SG or higher
classification except oils
labeled as energy
conserving on the
circular API
service label
viscosity SAE 10W-40
(weight)
JASO T 903 MA
standard
suggested oil
Pro Honda GN4 or HP4 (without
molybdenum additives) 4-stroke
oil (USA & Canada), or Honda
4-stroke oil (Canada only), or an
equivalent motorcycle oil.
＊
Suggested oils are equal in performance
to SJ oils that are not labeled as energy
conserving on the circular API service
label.
www.ClassicCycles.org
Engine Oil & Filter
＊
Servicing Your Honda
91