Honda VTX1800R Owner's Manual page 90

Your motorcycle does not need oil
additives. Use the recommended oil.
Do not use oils with graphite or
molybdenum additives. They may
adversely affect clutch operation.
Do not use API SH or higher oils
displaying a circular API ''energy
conserving'' service label on the
container. They may affect lubrication
and clutch performance.
NOT RECOMMENDED
Do not use non-detergent, vegetable, or
castor based racing oils.
Other viscosities shown in the following
chart may be used when the average
temperature in your riding area is within
the indicated range.
OK
Engine Oil & Filter
Servicing Your Honda
81