It is recommended that engine coolant be changed seasonally. In order to work properly, an engine's cooling system and radiator need to be clean. After time, deposits build up and can clog the radiator. Changing engine coolant seasonally helps keep the cooling system clean.
Maintaining the proper coolant level in the radiator between changes is important to the longevity of the cooling system. One should never open the radiator cap while the engine is hot. Opening the radiator cap while the engine is hot allows pressurized hot coolant to shoot from the opening with force. Coolant is deadly to animals if consumed. When changing engine coolant, one should drain it into a container and dispose of it appropriately.