The cooling system is factory-filled with antifreeze, which can remain in it all year round. When mixing antifreeze with water, an equal ratio of water and antifreeze should be achieved. To protect the system down to -50°C, mix 50% water and 50% antifreeze. It is recommended to use antifreeze sold by Mercedes, as its chemical composition is specially selected for engines. To fill the cooling system of a 2.3-liter engine, 7 liters of coolant are required, and a 2.9-liter engine requires 7.5 liters.