In response, JASO introduced the T903 standard in 1998, a globally accepted benchmark for 4-stroke motorcycle oils. This standard stipulates the necessary performance levels for optimal motorcycle design lubrication.

The JASO T903 specification includes two performance categories:

JASO MA: Suitable for motorcycles with a wet clutch, these oils deliver the necessary friction performance without friction modifiers, preventing clutch slippage. They are appropriate for 4-stroke motorcycle engines employing a single oil system for the engine, gearbox, and clutch. MA oils are suitable for all applications.

JASO MB: Designed for motorcycles with automatic transmissions (scooters), these oils offer the required friction performance with added friction modifiers, promoting fuel economy. Classified as the lowest friction oils in 4-stroke motorcycle oils, MB oils should only be used in scooters, as they may cause clutch slippage in motorcycles.

An oil’s classification as MA or MB hinges on the results of the JASO T903 Clutch Friction test. This test evaluates three friction performance areas, ensuring the oil’s suitability for wet clutch applications: dynamic friction, static friction, and stop time.

In 2006, the JASO MA specification was expanded to include MA1 and MA2 categories. The difference between these two lies in the higher friction performance delivered by MA2 oils. Thus, from 2006 onwards, oils conforming to the T903:2006 standard can be categorised into four specifications for 4-stroke motorcycle oils:

JASO MA: Standard specification oils for integrated oil systems (where the engine, gearbox, and clutch use the same oil). These oils don’t contain friction modifiers.

JASO MA1: A lower standard specification for motorcycles that use separate oils for the engine, gearbox, and clutch.

JASO MA2: A higher standard specification suitable for modern motorcycles, especially those with catalytic converters in the exhaust system.

JASO MB: A lower standard specification intended for scooter engines.

For an oil to qualify for any of the JASO specifications, it must meet at least one of the following quality levels:

API SG, SH, SJ, SL, SM
ILSAC GF-1, GF-2, GF-3
ACEA A1/B1, A3/B3, A3/B4, A5/B5, C2, C3

In addition to these widely recognised motorcycle oil specifications, JASO introduced a rating system for 2-stroke oils in 1994, designed for modern 2-stroke motorcycles and scooters which necessitate less ash-producing oil.

The JASO 2-stroke oil classifications are:

JASO FA: The lowest specification, testing lubrication capability, detergency, initial torque, exhaust smoke, and exhaust system blocking. Declared obsolete in 2005, it is still in use.

JASO FB: A slightly higher specification than JASO FA, requiring increased lubrication capability, detergency, exhaust smoke, and exhaust system blocking.

JASO FC: Requires the same test results for lubrication capability and initial torque as JASO FB but with higher standards for detergency and exhaust smoke and exhaust system blocking.

JASO FD: Has the same standards as JASO FC with a higher requirement for detergency.

It’s essential to refer to your vehicle’s owner’s manual to determine the required specification. If both an API and JASO MA specification are listed, ensure your chosen oil meets both specifications.