4. Oil specifications for 2-stroke engines

4.1 Special features of 2-stroke engines

Spark-ignition 2-stroke engines, whether water-cooled (outboard engines) or air-cooled (engines used in mopeds, motorcycles, scooters, chainsaws, lawnmowers, brushcutters, etc.), often operate at high temperatures. They are always fitted with a dry sump, since this is used to transfer the air-fuel mixture to the cylinder via the intake ports. Burnt gases, pushed by fresh gases, are evacuated through exhaust ports. The air-fuel mixture is used to lubricate moving parts, since it comes into contact with all the surfaces to be lubricated during transfer. To achieve this, the oil is mixed with the gasoline, either by micro-injection using a metering pump (separate lubrication) at the carburetor or fuel injection pump outlet, or, more simply, by...