Do I need to drain the old coolant when replacing it?

[Sheldon]

If the color is the same, there's no need to drain it; if different, then it should be drained. How to determine coolant: If the original antifreeze and the antifreeze you want to add have different compositions, then it must be drained and cannot be mixed. If the antifreeze hasn't been replaced for more than 3 years, it is recommended to drain it completely before adding new coolant. Coolant replacement interval: Coolant should be replaced every two years or 40,000 kilometers, depending on the actual usage of the vehicle. For commercial vehicles like taxis, which are used frequently and cover more mileage, the coolant needs to be replaced more often. The full name of coolant is antifreeze coolant, which has antifreeze properties. It prevents the coolant from freezing in cold seasons, which could otherwise crack the radiator and damage the engine block.