Fluids and filters for the 5.9L 1998.5–2000 Cummins Marine engine ensure clean and efficient operation. Engine oil lubricates moving parts and reduces wear. Coolant regulates engine temperature and prevents overheating. Fuel filters remove contaminants to protect injectors and fuel system. Oil filters trap impurities, maintaining oil cleanliness. Proper maintenance of fluids and filters extends engine life and reliability.