API two-cycle oil categories: historical status
API TA, TB, TC and TD are legacy two-cycle gasoline-engine oil designations. They remain useful when interpreting older manuals, containers and product literature, but API does not present them as current categories in its Engine Oil Licensing and Certification System. An API TC statement on a modern product should therefore be treated as a legacy performance claim, not as evidence of a current API licence or certification.
| Specification | Status | Historical application |
|---|---|---|
| API TA | Obsolete | Entry-level category historically associated with very small air-cooled two-stroke engines, including mopeds and similar utility equipment. |
| API TB | Obsolete | Historical category for more highly loaded small two-stroke engines, including scooters and motorcycles. |
| API TC | Legacy; not an active API licensing category | Historically used for higher-performance, non-marine two-stroke engines, particularly air-cooled motorcycle, snowmobile and utility applications. It was associated with control of piston deposits, ring sticking, pre-ignition and scuffing. It was not a water-cooled outboard category. |
| API TD | Obsolete | Historical category for water-cooled two-stroke outboard engines. It is not the current marine qualification; use the oil requirement specified by the engine manufacturer. |
Current standards relevant to two-stroke oils
For non-marine crankcase-scavenged two-stroke gasoline engines, current product literature and manufacturer documentation may instead specify ISO two-cycle oil categories EGB, EGC or EGD, or JASO oil classifications FB, FC or FD. ISO 13738:2011 remains current following its 2022 confirmation. JASO M345:2024 classifies two-cycle oils as FB, FC and FD; FC adds low-smoke and exhaust-system-blocking performance over FB, while FD adds higher-temperature detergency performance over FC.
For water-cooled two-stroke marine engines, NMMA TC-W3® is the active marine performance-based qualification program. TC-W3® is not interchangeable with an air-cooled-land-engine requirement merely because a product also makes an API TC claim.
Always use the oil type, performance level, viscosity or mix ratio stated in the current engine manufacturer documentation. A later-looking category or a broad multi-application label is not automatically suitable for every two-stroke engine.
For API’s current automotive engine-oil categories and licensing marks, see the API Engine Oil Service Category Charts.