To reduce the management cost and environmental load of water-soluble coolant, authors have been studying on a metabolic system for water-soluble coolant. More than 90% of waste water-soluble coolant is composed of water phase. If the oily additives and contaminants can be isolated from the waste coolant, the amount of waste coolant decreases remarkably because the recycled water can be reutilized as a diluent of renewal coolant. Authors has been developed some types of water recovery methods for the metabolic system. To complete the metabolic system for water-soluble coolant, the coolant diluted with recovered water should have the same machining performance and long-term stability as those of coolant diluted with tap water. In this report, we examined the machining performance and ability change of water-soluble coolant diluted with recycled water under operations encountered in machine tool.