Honda NRX1800 2004 Owner's Manual page 201

Specifications
Fuel & Lubricants
fuel
recommendation
fuel tank capacity
engine oil capacity
engine oil
recommendation
final drive oil capacity
cooling system,
recommendation
cooling system,
capacity
192
Technical Information
unleaded gasoline, pump octane number of 91 or higher
6.08 US gal (23.0 )
after disassembly:
after draining:
3.8 US qt (3.6 )
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
after draining: 4.2 US oz (125 cm )
Pro Honda HP Coolant or an equivalent high quality ethylene
glycol antifreeze containing corrosion protection inhibitors
specifically recommended for use in aluminum engines
5.1 US qt (4.8 )
4.9 US qt (4.6 )
3.9 US qt (3.7 )