ISO two-cycle oil specifications
ISO 13738:2011 is the current International Standard for lubricating oils used in crankcase-scavenged, spark-ignition two-stroke engines. Its intended applications include motorcycles, snowmobiles, chainsaws and other transportation, leisure and utility equipment. The standard specifies requirements for the ISO-L-EGB, ISO-L-EGC and ISO-L-EGD categories defined within the ISO engine-oil classification system.
These ISO categories arose from international work that built on the earlier JASO two-stroke-oil system. The global development added a longer-duration detergency and piston-cleanliness evaluation to the established lubricity, detergency, smoke and exhaust-system-blocking assessments. This history explains why ISO-L-EG labels are often seen alongside JASO claims on two-stroke-oil packaging.
ISO-L-EGB, ISO-L-EGC and ISO-L-EGD are ISO performance categories, not viscosity grades, fuel-mix ratios or manufacturer approvals. Use the oil grade, mixing ratio and any product-specific approval required in the current engine or vehicle manufacturer documentation.
Current ISO categories
| ISO category | Status under ISO 13738:2011 | Historical relationship to JASO categories |
|---|---|---|
| ISO-L-EGB | Active ISO category; the first of the three ISO-L-EG categories. | Historically associated with the JASO FB performance level, with the additional global piston-cleanliness/detergency assessment. |
| ISO-L-EGC | Active ISO category; above EGB within the ISO-L-EG sequence. | Historically associated with JASO FC, again with the additional global piston-cleanliness/detergency assessment. |
| ISO-L-EGD | Active ISO category; the highest category specified by ISO 13738:2011. | Historically associated with JASO FD and the most demanding ISO-L-EG detergency and piston-cleanliness requirements. |
Relationship with JASO
The current JASO two-stroke standard is JASO M345:2024, which continues the FB, FC and FD performance classifications. Its 2024 revision addressed changes to exhaust-smoke-density evaluation equipment. Because JASO test procedures and implementation requirements have been revised over time, an older shorthand such as “ISO-L-EGD equals JASO FD” should be treated as historical context rather than proof that one current claim automatically satisfies the other. Where a manufacturer specifies one designation, use an oil that expressly claims that designation.
For the JASO classifications themselves, see JASO oil specifications. The older API two-cycle categories are a separate system; see API two-cycle motor oil specifications.
Current and historical status
Current: ISO 13738:2011, second edition, published in July 2011 and confirmed by ISO in 2022.
Withdrawn: ISO 13738:2000, replaced by ISO 13738:2011.
Not an ISO 13738:2011 category: JASO FA and references to proposed or historical ISO-L-EGE material should not be presented as active ISO 13738 categories.