Honda TRX450ER Owner's Manual page 102

Engine Oil Recommendation
API classification
viscosity (weight)
suggested oil
Motor oils intended for Service SE, SF or SG will show this
designation on the container.
Your ATV does not need oil additives. Use the recommended oil.
Do not use API SH or higher oils displaying a circular API ''energy
conserving'' service label on the container. They may affect
lubrication.
NOT RECOMMENDED
Do not use non-detergent, vegetable, or castor based racing oils.
Engine Oil & Filter
SE, SF or SG
SAE 10W-40, 5W-30
Honda 4-stroke oil or an equivalent
OK
Servicing Your Honda 93