The JASO T903:2023 specification for four-stroke motorcycle oils has been released. Here we discuss the key drivers and purpose of the revision, what changes are being made and what this means to key stakeholders.

The Japanese Automobile Standards Organization (JASO) small engine specifications continue to be adopted globally by the industry as key performance standards for both 2-stroke and 4-stroke applications.

For 4-stroke applications, JASO introduced the T903 specification in 1998 as a global standard; ensuring approved motorcycle oils simultaneously meet minimum performance requirements for the engine, clutch and gears. Since that time regular revisions to the specification have followed, the last in 2016, to ensure the standards remain relevant to the latest motorcycle hardware requirements.

This new release is the fifth revision to the JASO T903 specification.

Market Drivers and Purpose of the JASO T903 Revision

As motorcycle markets around the world continue to legislate for tighter and tougher emissions standards, the move from carburetor to port fuel injection technology has been widely adopted by OEMs as an enabling technology for lower emission hardware. This change has also enabled increased engine power densities, resulting in more severe engine oil operating conditions. As a consequence, there is a need for increasingly robust piston cleanliness performance as well as improved oxidative and thermal stability.

In addition to the engine upgrades for lower emission hardware, the tighter emission norms have also driven adoption of highly efficient three-way exhaust after-treatment catalysts. With the latest emission standards requiring in-use emissions conformity for the effective vehicle lifetime, catalyst durability and specifically catalyst compatibility with the engine oil are now key new performance requirements. Phosphorus originating from the engine oil can however act as a poison to the precious metal active sites in the exhaust catalyst, thereby rendering it less effective over time. Additionally, phosphorus volatility (evaporation loss) is found to be higher in motorcycles due to the higher operating temperatures the oil is exposed to. As a consequence, there is a need to minimize catalyst exposure to phosphorous from the oil, while at the same time ensuring no compromise in the protection the oil delivers to the engine hardware.

The new specification revision seeks to address these points, and also update the friction material used in the clutch friction test to keep it representative of the friction material being commonly used in the latest hardware designs.

The JASO T903:2023 Revision

Formally named “Motorcycles – Four-Stroke cycle gasoline engine oils (JASO T903:2023)”, the fifth revision to the T903 specification includes changes to the following:

1) Engine Oil Quality Standards

To meet the latest hardware needs and the resulting increased severity in oil operating conditions, the American Petroleum Institute (API) SG and SH categories have been removed from the new JASO specification to upgrade the minimum level of crankcase performance. This is to ensure adequate protection against build-up of engine sludge, oxidation or wear in the latest hardware applications. This means the minimum crankcase performance level for new registered formulations will be API-SJ, in line with current API standards. Also in line with the latest API oil classifications, the JASO specification has been updated at the upper end of the performance range to include API SN Plus as well as API SP. These categories provide further performance benefits including emissions system compatibility, oxidative stability and deposit control for the most severe modern hardware applications.

At the same time, crankcase performance standards from ACEA or ILSAC have been removed from the category lists, given there have been very few submissions from oil marketers in previous years based on these core specifications.

2) Changes in the Phosphorus Content and Evaporation Loss

To enhance durability of the motorcycle three-way exhaust catalyst, the phosphorus upper limit has been reduced from 0.12mass% to 0.10mass%. The minimum level of 0.08mass% remains unchanged in order to not compromise wear protection and gear pitting performance. The reduced limit of evaporation loss from 20 max to 15 max ensures improved performance against oil consumption.

3) Clutch Friction Characteristic Test

The friction plate material used in the SAE#2 test, which measures friction performance of the clutch, is being upgraded to ensure it is representative of the latest friction material being commonly used in modern hardware. There is also a change in the reference oils used in the test due to availability and to ensure continuity of supply through the duration of this specification revision.

JASO T903:2023 Timing

JASO T903:2023 specification was released on May 8th 2023
Oil marketers able to commence first licensing from October 1st 2023
For JASO T903:2016 new applications can be made until September 30th 2023
Current valid T903:2016 on file data will be expired by April 30th 2028

Our View

The release of JASO T903:2023 better reflects the requirements of modern hardware and aftertreatment devices, reduced emission requirements and the increase in operational severity of today’s motorcycle oils. Removing API SG and SH categories means API SJ becomes the minimum performance level to meet the revision. With the addition of the highest performance level API SN Plus and SP categories, the revision supports a real performance upgrade opportunity for markets around the world.

The trend toward use of lighter viscosity oils for increased fuel efficiency reduces oil film strength and places increased stress on the additive anti-wear system. This has the potential to give rise to wear durability issues, however formulating to counter this is made more challenging by increased restrictions in phosphorus content. The need to deliver enhanced catalyst compatibility effectively limits the use of conventional anti-wear chemistry. This requires the use of novel anti-wear components and a different formulating approach to ensure a balanced approach to deliver the performance, efficiency, durability and catalyst compatibility required by the latest hardware.

For oil marketers, the first point of note is that any formulations registered under the T903:2011 version of the specification will soon expire and will need to be upgraded. Formulations registered under the T903:2016 version will be valid until 2028 meaning that there is no immediate need to upgrade existing registered formulations. Going forward, offering JASO T903:2023 approved motorcycle oils will ensure both current and future hardware oil performance requirements can be met as part of an effective and future-proofed product portfolio.

For more information on motorcycle oils, contact your Lubrizol representative.

JASO T903:2023 Motorcycle Specification is Here