The Komatsu PC300-5 and PC300LC represent robust and reliable heavy machinery, designed for demanding excavation and construction tasks. These models, part of the 5th generation, are engineered for superior performance and durability, featuring powerful S6D108-1 and SA6D108-1 diesel engines that deliver substantial gross power and torque. With a hydrostatic transmission, a considerable operating weight, and impressive digging capabilities including a maximum digging depth of 6700 mm and a standard bucket capacity of 1.4 m³, the PC300-5 and PC300LC are built to handle challenging job sites efficiently. Their substantial dimensions, including a length of 10740 mm with the bucket and a width of 3290 mm, underscore their capacity for large-scale operations. This comprehensive manual provides essential information for the operation, maintenance, and repair of the Komatsu PC300-5 and PC300LC excavators. It covers critical areas such as detailed maintenance procedures, including engine oil and hydraulic system capacities, troubleshooting guidance, and technical specifications for the engine, transmission, and overall machine. The manual is structured to assist owners, technicians, and mechanics in ensuring the optimal performance, longevity, and safety of their equipment. With three distinct manuals included, covering various aspects of the machine and its S6D108-1 engine series, users will find the necessary resources to effectively manage and service these powerful excavators.