After a lengthy development cycle, the JASO Engine Oil Standards Implementation Panel issued in May 2023 the highly anticipated JASO T903:2023 standard for four-stroke motorcycle engine oils. Taking effect October 1, 2023, the new standard addresses issues such as clutch slippage and wear due to transmission gear pitting as the demand for lower viscosity oils increased to achieve better fuel economy.

The new standard arrives at a time when two-wheeled transportation is growing in popularity, especially in Asia, which accounts for around 80% of the global motorcycle market. At the same time, motorcycle OEMs have been modifying engine designs in response to stricter CO2 emission control and fuel efficiency standards. Today’s engines are more compact and complex, with tighter tolerances between moving parts, high power density, and hotter operating temperatures. Increased stress on the engine oil due to stricter emission standards and the resulting changes to motorcycle engines are the chief drivers behind the new JASO spec.  

New friction performance testing standards: The most significant is the revision of classification thresholds due to the changes in reference oil and the shape of friction material used for friction property testing due to supply continuity issues. It changes the friction index ranges for JASO MA, MA1, and M2 for motorcycles with a wet clutch and JASO MB for scooters with a dry clutch.

Engine oil quality: Introduced the API SN PLUS and API SP categories. At the same time, some lesser-used oil categories, including API SG, SH, ILSAC, and ACEA standards, were deleted because there was no record of on-file notification. The new list includes API SJ, SL, SM, SN, SN PLUS, and SP. 

Tighter phosphorous limits: Another change is tightening maximum phosphorous limits from 0.12% to 0.10%. It reflects the majority of T903:2016 on-file oils listed in October 2019. It is aligned with a trend toward lowering phosphorous content to protect exhaust after-treatment systems. 

Noack volatility limits: Tightening the Noack volatility from 20% to 15% maximum means less oil consumption and helps improve lower viscosity oil performance, which further helps in CO2 reduction.

In summary, the new specification addresses four critical factors of the modern motorcycle lubricant – 

1. CO2 emissions: Lower viscosity oils are required to deliver fuel economy benefits to meet the lower CO2 emission regulations.

2. Durability: The increased necessity to protect the engine, clutches, gears, valve train, and after-treatment systems. 

3. JASO classification: Defines the frictional characteristics required for the oil. 

4. API performance: Used in tandem to enhance durability through piston cleanliness, deposit control, and thermal stability. 

It is becoming even more critical for the lubricant marketer and their additive partners to address the diverging needs of modern motorcycle oil, which differs significantly from modern passenger car motor oils. Modern motorcycle oil needs to:  

• Meet the diverging phosphorous limit between API (0.08wt% max) and JASO (0.08wt% min).   

• Deliver engine durability and protect after-treatment catalyst durability.  

• Deliver strong frictional properties for enhanced clutch performance. 

• Avoid gear pitting while using low-viscosity oils.

As a major motorcycle engine oil additive supplier, Chevron Oronite is ahead of the game. In anticipation of JASO T903:2023, we introduced OLOA 22028T, a differentiated next generation four-stroke motorcycle additive that meets the current JASO T903:2016 standard as well as the new JASO T903:2023 standard taking effect starting October 1, 2023. It also meets the latest API SP standards. 

OLOA 22028T has undergone an intensive 100-hour engine durability test, which conclusively proved that motorcycle oils formulated with this technology deliver excellent protection for engines, clutches, gears, and valve trains. Compared to reference oils, the solution has also demonstrated strong friction performance in extended frictional durability testing.

Published: November 2023