Honda TRX300EX Owner's Manual page 103

Engine Oil & Filter
Other viscosities shown in the following chart may be used when the
average temperature in your riding area is within the indicated range.
JASO T 903 standard
The JASO T 903 standard is an index for engine oils for 4-stroke
motorcycle engines.
There are two classes: MA and MB.
Oil conforming to the standard is labeled on the oil container. For
example, the following label shows the MA classification.
(1) code number of the sales company of the oil
(2) oil classification
Servicing Your Honda
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(1)
(2)