According to proper practices, what type of coolant should be used when refilling the cooling system?

Using the coolant recommended by the vehicle manufacturer is essential for maintaining optimal engine performance and longevity. Manufacturers specify particular coolant formulations that include specific additives designed to protect engine components and ensure proper thermal management. These additives can vary significantly between different coolant types and are tailored to the materials used in the engine and cooling system, which can include aluminum, cast iron, and various plastics.

The recommended coolant may have specific properties, such as rust inhibitors, boil-over protection, and freeze protection, which allow the engine to operate under a wide range of conditions. Additionally, using the manufacturer's recommended coolant helps prevent issues like corrosion, scale buildup, and overall system failure, which can occur if incompatible coolants are mixed or if the wrong type is used.

While universal coolants may claim compatibility with a variety of vehicles, they might not provide the same level of protection as the specific formula outlined by the manufacturer. Likewise, choosing coolant based solely on color or any type might lead to potential mismatches in chemical properties, thus compromising the cooling system's functionality. Therefore, for optimal performance and protection, utilizing the coolant specified by the vehicle manufacturer is the most prudent choice.