In 4-stroke engines at each oil change; in 2-stroke engines, add when filling the oil/fuel tank. Shake well before use! Dosage: In 4-stroke engines or the transmission: 20ml (1 tube) is sufficient for 1liter (1 qt) of motor oil. In 2-stroke engines (mixture lubrication): 10ml per 10liters (3 gal.) of fuel mixture or 20ml for 400ml (13.5 FL OZ) of 2-stroke oil with separate lubrication.