Ethylene glycol is a widely used coolant and antifreeze fluid that plays a vital role in maintaining a vehicle’s engine temperature under both extreme heat and cold conditions. Chemically represented as C₂H₆O₂, it is a clear, colorless liquid with a slightly syrupy consistency and a sweet odor, though it is highly toxic if ingested and requires careful handling. Mixed typically in a 50:50 ratio with water, ethylene glycol significantly lowers the freezing point and raises the boiling point of the engine’s coolant, ensuring reliable performance in sub-zero temperatures as well as preventing boil-over during hot weather. In addition to temperature regulation, it contains corrosion inhibitors that protect the radiator, hoses, and engine components from rust and scale buildup, thus extending engine life and improving efficiency. Its high heat transfer capability ensures the engine operates at an optimal temperature, reducing the risk of overheating and engine damage. With a service life of about 2–5 years, ethylene glycol requires regular maintenance checks to maintain its effectiveness. While it is the most common coolant type, alternatives like propylene glycol are sometimes used due to lower toxicity. As it is harmful to the environment and living beings, proper disposal is critical. Overall, ethylene glycol is an indispensable fluid for safe, efficient, and long-lasting engine performance.