Abstract
In the conventional system of lubrication, lubricating oil is renewed with fresh oil after it is used for some period. Accordingly, waste oil is generated in the conventional system. The authors have developed a new system that makes it possible to use lubricating oil semi-permanently without oil renewal. In the new system, therefore, no waste oil is generated and it is enough to supply only a small amount of fresh oil sometimes to compensate for the lost oil. This system has been working well in about one thousand units of marine and cogeneration diesel engines in practice. The new system always keeps lubricating oil clean as the kidney of animals always keeps their blood clean. This is why lubricating oil can be used semi-permanently and the new system is called kidney system. This technology has been developed based on the assumption that lubricating oil is hardly oxidized contrary to the general knowledge all over the world. This report verifies the above mentioned assumption based on our analysis of used oil in engines in practical use and some data in various fields.
