Coolant is a heat-transfer fluid circulating within a vehicle’s engine and often throughout other systems to regulate operating temperature. Primarily utilized in the water jackets of engine blocks and cylinder heads, it absorbs heat generated by combustion and radiates it through the radiator. Formulations are typically ethylene glycol or propylene glycol-based, incorporating corrosion inhibitors, anti-foam agents, and dye for leak detection. Specific types vary in silicate/borate content and are designated for use with specific metallurgy, requiring compatibility with seals and materials. Extended-life coolants offer prolonged service intervals due to advanced inhibitor technologies.