This manual covers the Komatsu PC300-6 and PC350-6 excavators, part of the Generation 6 series. These machines are engineered for demanding construction and earthmoving applications, featuring robust construction and reliable performance. The PC300-6, with an operating weight of 30800 kg and a digging depth of 7120 mm, is suited for general excavation tasks, while the larger PC350-6, weighing 34500 kg and offering a reach at ground level of 10665 mm, is designed for more extensive projects. Both models are powered by the Komatsu SAA6D108E-2 diesel engine, delivering substantial power for efficient operation. This comprehensive Operation and Maintenance Manual, presented in English, provides essential information for the upkeep and repair of your Komatsu excavators. It details critical maintenance schedules, including oil change intervals of 250 hours, fluid capacities for engine oil, hydraulic oil, and coolant, and outlines various technical specifications. The manual is structured to assist owners, mechanics, and technicians in understanding the machine's systems, performing routine maintenance, and troubleshooting potential issues to ensure optimal performance and longevity.