The Japanese Society of Automotive Engineers announced that it has updated its JASO T 903 performance specification for four-stroke motorcycle engine oils. The revised specification—which was published on the Japan Lubricating Oil Society’s website earlier this year and is the fifth revision to the specification since its conception in 1998—now incorporates the latest API passenger car motor oil standards. This addition was made in an effort to protect gears and other equipment as the market trends toward lower-viscosity and lower-friction lubricant products.
The update became public in May after adoption by JSAE. The JASO specification—which is the world’s most-used motorcycle oil standard—was last updated in 2016.
Why Is an Update Needed?
As with previous versions, the updated JASO specification—officially known as JASO T 903:2023, or “Motorcycles Four-Stroke Cycle Gasoline Engine Oils”—incorporates requirements of passenger car motor oil standards. However, it necessarily incorporates other parameters. One notable addition is a test that measures an oil’s ability to provide the friction performance needed to protect the motorcycle’s unique clutch system.