New JASO T903 motorcycle specification
04 July 2023
07 June 2016
What’s new in the latest revision of the four-stroke motorcycle lubricant specification?
The latest revision of the JASO T 903 specification will help to ensure future motorcycle lubricant formulations continue to deliver sufficient protection to four-stroke machines. Insight looks at the key drivers for the 2016 revisions, examines the main changes and explores why Infineum believes the inclusion of a well-defined test to guard against gear pitting is increasingly important.
With Japan’s position as a major motorcycle manufacturing country, the Japanese Standards Organization (JASO) has led the development of four-stroke (4T) motorcycle oil (MCO) standards. The first 4T gasoline engine oil standard, introduced in 1998, was driven by the widening gap between the lubrication requirements of motorcycles and passenger cars.
As industry lubricant specifications for cars introduced fuel economy requirements, they tended towards lower viscosity and lower friction. This trend raised concerns that the use of these thinner, often friction modifier containing, oils in motorcycles with wet clutch systems could cause clutch slippage and transmission gear pitting wear. In response, the Society of Automotive Engineers of Japan (JSAE) established the JASO T 903 standard, which sets quality limits as a basic measure to ensure oils deliver adequate protection to today’s motorcycles.
The JASO T 903 specification has three major requirements: physical properties, engine oil performance and clutch friction characteristics.
The clutch friction requirements categorise oils as high friction JASO MA/MA1/MA2, or low friction JASO MB, and are central to the standard. The standard was revised in 2002, 2006 and 2011 to ensure JASO certified lubricants continue to deliver the required level of motorcycle hardware protection.
Following the 2011 revisions, reports from several oil suppliers suggested that some low friction MB oils containing friction modifiers were categorised as JASO MA/MA1. The Japan Automobile Manufacturers Association (JAMA) MCO Working Group confirmed these views, raising the concern that market quality issues due to clutch slip may arise.
Another driver was the desire to reduce the amount of friction modifier required to meet MB, to help address the concerns that solubility issues could lead to sediment formation, which might cause issues for scooter applications.
These challenges, along with the need to update friction plates and reference oils, led JAMA MCO WG to start work on updating the specification. After a considerable amount of industry effort, the revised JASO T 903:2016 specification was released at the end of April.
For the 2016 specification, JASO has introduced new clutch friction plate materials and new reference oils to discriminate oil performance more clearly. In addition for JASO T 903:2016 the limits for friction severity have been set back to the 2006 level to prevent MB oils from being able to achieve MA performance.
The first allowable use of the new JASO specification will be October 1 2016.
There will be an overlapping period, when oil marketers will be allowed to file according to the 2011 or the 2016 standard. The last date when a new notification can be accepted for the 2011 standard is September 30 2016 and the expiration of the on-file data is set for April 30 2021.
Changes to the specification mean that resources will be needed to test and reapprove currently certified oils. An increase in the severity, in terms of friction performance, is expected for MA oils to prevent low friction MB oils containing friction modifiers from being categorised as JASO MA/MA1. For MB oils, there is likely to be an improvement in the stability of the formulation package, which should need less friction modifier to meet the JASO T 903:2016 requirements.
Now that the specification has been released and the friction materials are available for testing Infineum is confident that the performance of its additive solutions will be confirmed. Work is underway to ensure we will be ready to help customers meet the latest specification.
JAMA had hoped that a gear pitting performance requirement would be incorporated into this revision, something they had requested since the specification’s inception. Unfortunately it has not been possible to develop an acceptable test in time for inclusion in the 2016 specification.
Infineum regards gear pitting as an important performance parameter. The development of a well-defined gear pitting test will enable clear differentiation between a properly formulated motorcycle oil, designed to protect the gears, clutch & engine, and a passenger car motor oil, designed only to protect the engine. When a test is included, there may no longer be a need for the current phosphorus requirement of between 800 ppm and 1,200 ppm. But, until then, the current limits will continue to serve the interim needs of the industry.
In our view, as fuel economy becomes more of an interest to motorcycle OEMs, the inclusion of a gear pitting test that is relevant to the wear conditions experienced in a motorcycle is increasingly important.
Currently most motorcycle oils are SAE 10W-40 but, we are already seeing a growing interest in lower viscosity grades. This trend makes wear control even more of a challenge and the gear pitting test is needed to ensure adequate hardware protection is delivered by these low viscosity oils.
The next JASO T 903 four-stroke specification update is expected in 2021, following the usual five-year cycle. Infineum expects the development of a reliable gear pitting test to be the number one priority for the next revision. Although there is still a long way to go to finalise the test, Infineum hopes that if an appropriate test can be developed in the next year or two JASO may not wait the full five years to bring it into the specification.