Development of 4-Stroke Motorcycle Oil

With the improvement of the national economic level, people are pursuing a more personalized lifestyle. Among some groups of car owners, the transportation attribute of motorcycles has gradually switched to leisure and entertainment functions, which has further driven the growth of the large-displacement motorcycle market.

 

In some developed countries and regions like the United States, Japan, and the European Union, the demand for motorcycles is mainly focused on medium and large-displacement motorcycle models, which are mainly used for entertainment. And the demand for large motorcycle displacements is also increasing in emerging markets like India and Malaysia.

 

At the same time, in the context of increasingly stringent energy-saving and environmental protection requirements, scooters are also popular for their driving comfort, convenience, and energy-saving performance. They are in great demand in the international market, especially in the Southeast Asian market, and the number of scooters in the Chinese market is also growing continuously.

 

 

Driven by the development of the high-end motorcycle market and technology, the demand for differentiated motorcycle oil performance is more prominent for models with different technical differences.

 

For 4T motorcycles with wet clutches, motorcycle oil needs to lubricate multiple components, such as the engine, clutch, and gearbox, simultaneously. Therefore, motorcycle oil is required to have suitable friction characteristics to ensure smooth starting and no clutch slippage. And it also needs to have good anti-shear performance, anti-wear extreme pressure performance, high temperature cleanliness performance, and thermal stability.

 

For motorcycles with dry clutches (such as most scooters), where the engine and transmission lubrication systems are independen,t and the clutch requires no lubrication, the scooter engine oil should possess a low friction efficiency to deliver better lubricating performance and energy saving.

 

For large-displacement motorcycles, the valve cam and valve rocker arm are subject to greater impact loads when the engine is working. The engine speed is higher, the temperature is higher, and the load is greater; therefore, the requirements for the anti-shear performance, anti-wear extreme pressure performance, high-temperature detergency performance, and thermal stability of motorcycle oil are also higher.

 

Based on the special requirements of performance, research has been conducted on the key properties of motorcycle oil. Specifically, the tribological characteristics, detergency and dispersion performance, and anti-wear extreme pressure performance of high-end motorcycle oil. As a result, motorcycle oil (four-stroke motorcycle oil) that meets the market demand of high-end motorcycles (four-stroke motorcycles) was developed.

 

4T Motorcycle Engine Oil Additive Package T3123

As a lubricant additives supplier in China, Chorus has insight into market demands and can provide lubricating oil additives specifically designed for 4-stroke motorcycle oil, which meet API SL, SJ, and other performance standards. At the same time, it also has many good performances, such as high temperature detergency, low temperature dispersity, anti-oxidation, anti-wear, and others. It has good compatibility with other base oils.

 

1. Specifications and Classifications of 4-Stroke Motorcycle Oil

At present, the international specifications for 4T motorcycle oil include the "Motorcycle-Four-Stroke Gasoline Engine Oil" formulated by JASO (Japan Automobile Standardization Organization): JASO T903 specification (current version is the 2023 version); ISO (International Organization for Standardization) formulated "Specification for oil use in Four-Stroke Cycle Motorcycle Gasoline Engines and Related Power Transmission Systems": ISO 24254 specification (current version is the 2007 version).

 

From the perspective of international recognition and wide application, the JASO T903 specification has wider recognition and wider application in the international scope. Currently, there is no national or industrial specification for four-stroke motorcycle engine oil in China. Domestic lubricant companies generally refer to or draw on the corresponding international specifications when producing four-stroke motorcycle oil.

 

Based on the quality grades of API and ACEA four-stroke motorcycle engine oil, and considering the characteristics of high engine speeds and the need to lubricate the clutch and transmission in 4T motorcycle engines, the JASO T903-2016 specification adds technical requirements related to shear stability.

 

"Motorcycle-Four-Stroke Gasoline Engine Oil": Special physical and chemical properties in the JASOT903-2016 specification

Item	JASO Quality Index	Method
Mass fraction of sulfated ash, %	≤1.2	JPI 2277
Evaporation loss, %	≤20	JPI-5S-41
Foam characteristics, mL/mL		JISK2518
Procedure I	<10/0
Procedure II	≤50/0
Procedure III	≤10/0
High temperature and high shear 150℃, 10°s-¹) viscosity/(mPa·s)	≥2.9	JPI-5S-36
Kinematic viscosity at 100℃ after diesel nozzle shear (30 cycles)/(mm²·s-1)	≥9.0(xW-30)	ASTM D6278
	≥12.0(xW-40)
	≥15.0(xW-50)
Other viscosity grades should maintain the viscosity requirements of this grade
Phosphorus wt%	0.08～0.12	JPI-5S-38

 

"Motorcycle-Four-Stroke Gasoline Engine Oil": Friction Characteristics Index in JASO T903-2016 Specification

Item	MA	MA1	MA2	MB	Method
Dynamic Friction Characteristics Index (DFI)	1.35～<2.50	1.35~<1.50	1.50～<2.50	1.50～<2.50	Appendix A of JASO T903-2016 Specification
Static Friction Characteristics Index (SFI)	1.45～<2.50	1.45～<1.60	1.60～<2.50	0.40～<1.45	Appendix A of JASO T903-2016 Specification
Stop Time Index (STI)	1.40～<2.50	1.40～<1.60	1.60～<2.50	0.40～<1.40	Appendix A of JASO T903-2016 Specification

 

Note: *If all three indicators of DFI, SFI, and STI meet MB, or one of them meets MB, and the other meets MA, or two of them meet MB and the other meets MA, it can be determined as the MB category. And if all three indicators are in MA, MA1, or MA2 at the same time, it can be determined as the corresponding category.

 

Here is a special explanation:

• The dynamic friction index (DFI) refers to a dynamic friction coefficient that simulates the relative friction sliding of the clutch plate when in contact; the static friction index (SFI) is a static friction coefficient that simulates the clutch plate when it is already in contact and fixed (no relative friction sliding occurs). The larger the static friction coefficient, the less likely the clutch plate is to slip under rapid acceleration conditions; the braking time index (STI) is a time index that simulates the clutch plate from separation to complete engagement and fixation. The larger the index, the shorter the time required for engagement and fixation.

 

• MA, MA1, and MA2 4-stroke motorcycle engine oils have a higher friction coefficient and are primarily suitable for wet-clutch motorcycles. They provide enhanced friction to prevent clutch slippage. In contrast, MB-grade oils feature a lower friction coefficient, designed for dry-clutch scooters to deliver better fuel efficiency.

 

2. Key Performance of Four-Stroke Motorcycle Oils

As mentioned above, for 4-stroke motorcycles with wet clutches, the clutch, engine, and transmission gears share the same lubrication system. Therefore, the 4-stroke motorcycle engine oil used should maintain a certain friction factor to prevent the clutch from slipping. And for four-stroke motorcycles with dry clutches, the lubrication of the engine and the lubrication of other components are independent systems. In order to meet the technical requirements of energy saving and emission reduction, it is necessary to moderately reduce the friction factor of oils in 4-stroke engines. Therefore, the technical key to developing four-stroke motorcycle oil is to adjust the friction characteristics and friction factor.

 

In addition, the cooling system of 4T engines is divided into two types: air cooling and water cooling. Compared with passenger cars, the cooling system has the characteristics of a large engine heat load and a small oil pan. Especially when air cooling is used, the working conditions are particularly bad. The oxidation products of gasoline and lubricating oil that are not fully burned will form deposits at high temperatures, affecting the normal use of the engine. Especially for high-end large-displacement motorcycles, the engine speed is higher, and the heat load is greater, so the requirements for high-temperature cleanliness and oxidation stability of four-stroke motorcycle oil are higher.

 

2.1 Friction Characteristics and Cleaning and Dispersing Properties

The friction factor of lubricating oil is affected by the oil film between the contacting surfaces. Polar molecules adsorb onto the metal surface or react with it to form a buffer film (lubricating film), which can reduce the friction and wear between metal friction pairs under high-load, high-speed, and high-temperature conditions.

 

Studies have shown that different types of anti-friction agents used in engine oil can reduce friction and wear, lower the friction coefficient, and save energy.

 

Based on the selected engine oil P1 and P2 technology platforms (API specification system technology platform), the feasibility of adjusting the friction factor of four-stroke motorcycle oil was studied.

 

Within the scope of the P1 and P2 technology platforms, boronized polyisobutylene succinimide dispersant (for simplicity, referred to as boronized dispersant, the same below) and dialkyl dithiocarbamate molybdenum (MoDTC) friction modifier were selected and added to motorcycle oil for research.

 

3. Conclusion

(1) For high-end 4-stroke motorcycles that use different clutch technologies (wet clutch or dry clutch), special motorcycle oils are needed. With the steady growth of the high-end motorcycle market, the demand for high-end motorcycle oils will also grow synchronously, which has a broad market potential.

 

(2) Drawing on the technical requirements and test methods in the "4T Engine Oil": JASO T903 specification, and based on the engine oil technology platform (P1 and P2 technology platforms), the friction characteristics of motorcycle oils were studied using MTM and verified by using the SAE No.2 test.

 

(3) When developing 4-stroke motorcycle oils, the technical solution of adding specific types of dispersants or friction modifiers to adjust the friction characteristics of motorcycle oils is feasible and effective.

 

(4) A series of four-stroke motorcycle oils whose friction characteristics meet the MA2 and MB categories in the "Motorcycle-Four-Stroke Gasoline Engine Oil": JASO T903-2016 specification was developed.

 

Chorus Lubricant Additives offers a range of 4-stroke motorcycle engine oils. Please contact our sales engineers to know more.