PURPOSE: To prevent seizure by providing a means, which forces passages to make open/close actions according to temperature of an engine so as to reduce viscosity of lubricant oil at low temperature, in an open/close means which opens/closes respective passages at a junction between a lubricant oil connection passage and a diluted liquid connection passage and adjusts a mixing state of lubricant oil and diluted liquid.

CONSTITUTION: An oil pump 2 is so connected as to forcibly feed fuel to a cylinder and a crank. A lubricant oil connection passage 8 for connecting a lubricant tank 4 to the oil pump 2 is provided and one end of a diluted liquid connection passage 10 of which other end is connected to a diluted tank 6 is connected on the way to the lubricant oil connection passage 8. An open/close means 12 which opens/closes respective passages 8, 10 and adjusts mixing state of lubricant oil and diluted liquid is provided at the junction of the lubricant connection passage 8 and the diluted liquid connection passage 10, and temperature sensing drive means 14 which makes the passages open/close according to temperature of the engine so as to reduce viscosity of lubricant oil at low temperature is provided in the open/close means 12 so that seizure may be prevented.