Honda 2006 RC51 Owner's Manual page 207

Specifications
Fuel & Lubricants
fuel
recommendation
fuel tank capacity
engine oil capacity
engine oil
recommendation
drive chain
lubricant
cooling system,
recommendation
cooling system,
capacity
200
Technical Information
unleaded gasoline, pump octane number of 91 or higher
4.76 US gal (18.0 )
after disassembly:
3.7 US qt (3.5 )
after draining:
after draining & oil filter change:
API Service Classification SG or higher except oils
labeled as energy conserving on the circular API service
label, SAE 10W-40, JASO T 903 standard MA,
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
SAE 80 or 90 gear oil
Pro Honda HP Coolant or an equivalent high quality
ethylene glycol antifreeze containing corrosion protection
inhibitors specifically recommended for use in aluminum
engines
3.1 US qt (2.9 )
Classic Cycles Technical Resources
4.5 US qt (4.3 )
4.1 US qt (3.9 )