Which substance raises the boiling point of water in the engine cooling system?

Antifreeze is specifically formulated to enhance the properties of water in the engine cooling system, including raising its boiling point. In a typical automotive cooling system, a mixture of water and antifreeze (often ethylene glycol or propylene glycol) is used. Adding antifreeze to water serves two primary purposes: it prevents the coolant from freezing in low temperatures and raises the boiling point, which helps in maintaining optimal engine temperature during operation.

This ability to raise the boiling point is critical because it allows the cooling system to operate more effectively under high temperatures generated by the engine. Water alone has a boiling point of 100 degrees Celsius (212 degrees Fahrenheit) at sea level, but when antifreeze is added, the boiling point can increase significantly, which prevents overheating and helps protect engine components from damage.

While oil, water, and fuel have essential roles in a vehicle, they do not serve the same purpose in this context concerning boiling point elevation in the cooling system. Therefore, antifreeze is the correct answer, as it is specifically designed to enhance the cooling properties of water, making it essential for engine temperature regulation.