Three application families, three different questions
JASO T 903 addresses four-stroke motorcycle engine oils and includes friction-related categories relevant to wet-clutch and transmission behaviour. JASO M 345 addresses two-stroke gasoline engine-oil performance. JASO M 355 addresses automotive diesel engine oils for Japanese engine and emissions-system needs.
The category letters cannot be compared vertically across those families. MA2 is not a higher version of an FC two-stroke category, and neither describes the same application as DH-2 or DL-1 diesel oil.
Read the edition, not only the letters
Standards and application manuals are revised. Test references, chemical limits, reference materials, filing dates and transition periods can change even when familiar category names remain visible.
A defensible product review records the full standard designation, publication year, viscosity grade, filing code where applicable and the date on which the on-file list was checked.
What the on-file system does and does not prove
JALOS maintains filed-oil lists and implementation manuals. The system supports consistent use of performance classifications, but JALOS has explicitly distinguished filing and self-certification from regulatory approval terminology.
A buyer should therefore verify the product code against the relevant list, check that the filing remains active and confirm the application against equipment-maker instructions. A label image alone is weak evidence.
Read the underlying documents.
- Motorcycle four-cycle gasoline engine oilJASO Engine Oil Standards Implementation Panel ↗
- Automotive diesel engine oil standardJASO Engine Oil Standards Implementation Panel ↗
- JASO engine-oil informationJapan Lubricating Oil Society ↗
Source links and status were reviewed on 31 July 2026. Standards and regulations may be revised after publication.