JASO T 903:2023 classifies four-stroke motorcycle oils as MA, MA1, MA2 or MB using 3 clutch-friction indexes: DFI, SFI and STI. Choose the SAE viscosity, API service category and JASO class specified in the exact motorcycle manual; those requirements vary by model and cannot be replaced by a general-purpose oil recommendation.
Choose motorcycle oil from the specifications in the exact owner’s manual, not the viscosity label alone. SAE viscosity, API service category and JASO friction class describe different parts of the oil requirement.
Compare the oil specifications
| Specification | What to match in the manual |
|---|---|
| SAE viscosity grade | Use the listed grade or temperature range. Some manuals show a viscosity chart. |
| API service category | Match the minimum or exact category stated by the motorcycle maker. |
| JASO T 903 class | Match the specified class: MA, MA1, MA2 or MB. The class uses 3 clutch-friction indexes. |
JALOS says JASO T 903:2023 classifies motorcycle four-cycle oils by dynamic friction (DFI), static friction (SFI) and stop-time (STI) indexes. MA1 and MA2 subdivide the MA ranges, while MB is the lowest-friction class among the four. These labels do not choose the viscosity for a specific engine.
Match the class the manual specifies
Use the manual’s oil table to check viscosity, API category and JASO class together. Do not assume that a higher-sounding class, a synthetic label or a familiar viscosity is a substitute for one of the required fields. Yamaha manuals illustrate how these values are model-specific: one manual lists API SE or higher and JASO MA or MB and shows a viscosity range by temperature.
Read the bottle and verify the application
Before buying, compare the full bottle label with the owner’s manual:
- Confirm the SAE viscosity and temperature range.
- Match the API service category.
- Match the JASO class when the manual specifies one.
- Confirm the oil is made for the intended four-stroke motorcycle application, then follow the manual’s oil-change interval and quantity.
For other maintenance choices, compare AGM and lithium powersports batteries and use our ATV and UTV tire sizing guide for off-road fitment and pressure. See our motorcycle stands and lifts comparison for service support choices. If a motorcycle needs to go to a service shop, use the motorcycle and ATV tie-down guide and truck ramp vs trailer comparison.
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Common questions
What does JASO MA mean in motorcycle oil?
JASO T 903:2023 uses three clutch-friction indexes to classify four-stroke motorcycle oils. MA is the broader class, with MA1 and MA2 subdivisions based on the measured index ranges.
What is the difference between JASO MA1 and MA2?
The JASO standard separates MA1 and MA2 across the same three friction indexes, with MA2 occupying the higher ranges. Use the exact class listed in your motorcycle manual.
Is JASO MB oil suitable for every motorcycle?
No. JALOS describes MB as the lowest-friction class among motorcycle four-cycle oils; check the manual's specified JASO class before buying.
Does SAE 10W-40 tell me which motorcycle oil to buy?
It gives the viscosity grade, but the manual may also specify an API service category and JASO class. Yamaha owner manuals, for example, list model-specific oil requirements and viscosity charts.