Classification of liquid lubricants used for lubrication of machinery equipment and tools in manufacturing industry. Includes industrial lubricating oils such as cutting oil, hydraulic oil, bearing oil, gear oil, compressor oil, turbine oil, and refrigeration oil. Targets liquid lubricants for friction reduction, cooling, and rust prevention of mechanical components including NC machine tools, CNC equipment, hydraulic machinery, pneumatic equipment, reducers, pumps, and compressors. Excludes grease and solid lubricants, handling only fluid liquid lubricating oils. Focuses on industrial lubricating oils compliant with ISO VG standards and JIS standards.