This classification covers specialized oils used as working media in hydraulic systems. It includes hydraulic fluids, lubricating oils, and seal protection oils used in hydraulic equipment such as press machines, injection molding machines, machine tools, and construction machinery. Key specifications directly related to hydraulic system performance and lifespan include viscosity grades (VG32, VG46, VG68, etc.), additive types (anti-wear, antioxidant, antifoam, etc.), temperature characteristics, and cleanliness levels. This category encompasses application-specific products such as ISO VG standard compliant oils, biodegradable oils, high-temperature resistant oils, and low-temperature fluidity oils, clearly distinguished from hydraulic equipment bodies, filters, and seal materials.