Two-stroke oil lubricates the engine and is burned with the fuel. It is different from four-stroke engine oil and from gear oil. It is added to the petrol (pre-mix) or fed from a tank by an oil injection pump.
What it does
It forms a film on the piston, cylinder and bearings. Oils from different makers differ in thickness and additives, so the ratio set by an engine maker was chosen for their own oil.
Signs it is wrong or failing
- Spark plug wet with oil, heavy smoke or a blocked silencer: too much oil, or a worn engine and seals. See Spark plug is wet with oil.
- Hot running or a seized piston: too little oil. See Engine has seized or locked up.
- The oil tank on an injection bike never goes down: Two-stroke oil tank level is not going down.
When to replace it
Use fresh oil in the tank and fresh pre-mix in the fuel tank. Do not keep pre-mix for months.
What to match when buying
- The oil and ratio in the manual. If a different oil is used, a richer ratio is the safe side.
- Use oil made for two-stroke engines. Do not use four-stroke oil.
- See Mix two-stroke pre-mix oil and petrol.