JASO engine-oil specifications
JASO standards are developed by the Society of Automotive Engineers of Japan (JSAE). For several engine-oil categories, the JASO Engine Oil Standards Implementation Panel operates an on-file system for suppliers that wish to use the applicable classification and oil-code marking. This is not a JASO product approval or certification: the supplier remains responsible for the oil’s quality, performance, and labeling.
The principal JASO classifications encountered on engine-oil labels are described below. A JASO grade is only one part of an oil requirement; always verify the viscosity grade, performance category, and any manufacturer approval specified in the current vehicle or equipment documentation.
Two-stroke gasoline-engine oils: JASO M345:2024
JASO M345 applies to lubricating oils for two-stroke gasoline engines, including motorcycle, utility-equipment, and outboard applications. The active edition is JASO M345:2024. It was revised in March 2024 in response to the end of manufacture and maintenance of the apparatus used for the former JASO M342 exhaust-smoke test.
The active performance grades are FB, FC, and FD. They address performance areas that include lubricity, cleanliness or detergency, deposits and exhaust-system blocking. A product’s mixing ratio and suitability for a particular air-cooled, water-cooled, injected, premix, marine, or utility engine remain equipment-manufacturer requirements; they are not set by the JASO grade alone.
| Grade | Status | Plain-English meaning |
|---|---|---|
| JASO FA | Obsolete | The original lowest historical grade. It is not part of the active M345 classification and should not be treated as equivalent to FB, FC, or FD. |
| JASO FB | Active | The entry grade in the current M345 system. |
| JASO FC | Active | A higher-performance grade than FB, historically associated with more demanding cleanliness, smoke, and exhaust-system-blocking performance. |
| JASO FD | Active | The highest current M345 grade, with more demanding detergency requirements than FC. |
Older containers and product literature may refer to earlier M345 editions during the implementation transition. For context on the relationship between the historical API two-cycle categories and later systems, see API two-cycle motor-oil specifications. For a grade-by-grade explanation, see JASO FB, FC and FD two-stroke oil standards.
Four-stroke motorcycle oils: JASO T903:2023
JASO T903:2023 is the active JASO classification for four-stroke motorcycle gasoline-engine oils. It was developed because low-viscosity, low-friction passenger-car oils can be unsuitable for motorcycles that share one lubricant between the engine, transmission, and wet clutch. The classification uses a clutch-friction test together with engine-oil performance and physical-property requirements.
| Grade | Plain-English meaning |
|---|---|
| JASO MA | The broad higher-friction motorcycle category. It is commonly relevant where the manufacturer specifies an oil compatible with a wet clutch. |
| JASO MA1 | A subdivision within the MA range, defined by clutch-friction index results. |
| JASO MA2 | A subdivision within the MA range with higher minimum clutch-friction indices than MA1. |
| JASO MB | The lowest-friction category among JASO four-stroke motorcycle oils. It must not be substituted where the manufacturer requires MA, MA1, or MA2. |
MA does not literally mean that an oil contains no friction modifiers; it identifies performance in the specified clutch-friction test. Likewise, an MB label does not by itself make an oil unsuitable for every motorcycle or scooter—use only the grade specified by the manufacturer. See JASO MA and JASO MB classifications for a fuller explanation.
Ultra-low-viscosity passenger-car gasoline oils: JASO M364:2025
JASO also maintains passenger-car gasoline-engine-oil classifications. The current JASO M364:2025 edition covers GLV-1 and GLV-2 ultra-low-viscosity fuel-economy oils. GLV-1 is associated with SAE 0W-8 and 0W-12 grades. GLV-2 is associated with SAE 0W-16 and 0W-20 grades and adds low-speed pre-ignition protection while maintaining GLV-1-level wear and high-temperature stability objectives.
In the JALOS on-file system, GLV-2 oils are identified as GLV-2A or GLV-2B according to the fuel-economy test method used. These classifications are for passenger-car gasoline engines, not a substitute for JASO T903 motorcycle-clutch classifications. See JASO GLV-1 and GLV-2 engine-oil standards.