Two-stroke motorcycle oils - JASO M345 standard

For two-stroke engines, lubricating oil performance is classified according to JASO. In 1994, the Japanese Automobile Standards Organization defined a specification (JASO M345-93) that described three quality levels for low-ash two-cycle engine oils: FA, FB, and FC. The standard was revised in December 2004 to include a new quality level - JASO FD and discontinuing JASO FA level. With these changes, JASO M345:2004 includes the following grades: FB, FC, and FD (in order to remain consistent with the ISO specification system). Lubricant performance is assessed according to five performance criteria: detergency, lubricity, initial torque, exhaust system blocking, and smoke. Performance of a candidate oil is rated against that of a reference oil. A key performance requirement of the JASO specification is the smoke requirement, which is especially stringent for the FC and FD performance categories. This requirement arises from the need to alleviate smoke problems in Asian cities. JASO FC and FD are the predominant performance levels.

The motorcycle oils industry is currently going through an important period of specification change. Major revisions have been proposed to the JASO M345 (for 2-stroke) motorcycle standards surrounding replacement of engine tests and inclusion of new engine tests. The JASO T903 (for 4-stroke) has recently been updated in 2016.

JASO M345:2004 Requirements

JASO Specification




Bench Testing

Flash Point, °C, min (D92/D93)    70 70 70
Kinematic Viscosity@ 100°C cSt, min (D445) 6.5 6.5 6.5
Sulphated Ash, % mass, max (D874)  0.25 0.25 0.18

Index Ratings

Lubricity, min (JASO M340) 95 95 95
Initial Torque, min (JASO M340) 98 98 98
Detergency1 (JASO M341)
Fundamental Part, min 85 95 1252
Piston Skirt Part, min   -- -- 952
Smoke, min (JASO M342) 45 85 85
Blocking, min JASO M343) 45 90 90

1 Index = (candidate oil/reference oil) × 100
2 Three hour test