Honda GL1800 2004 Owner's Manual page 135

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 to choose engine oils for 4-stroke
motorcycle engines.
There are two classes: MA and MB.
Oil conforming to the standard has the following classification on the oil
container.
(1) code number of the sales company of the oil
(2) oil classification
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Servicing Your Honda
(1)
(2)