Certificate of Qualification (C of Q) 310T Truck and Coach Technician – Engine Practice Test

A 50/50 solution of ethylene glycol (EG) and distilled water is often considered the most effective for engine protection due to the balanced properties it provides. This mixture ensures optimal freeze protection as well as effective boiling point elevation, which is crucial for maintaining engine performance under varying temperature conditions.

Using a 50/50 ratio creates a mixture that offers significant protection against freezing while providing sufficient heat transfer capabilities needed to keep the engine cool during operation. It helps to prevent corrosion within the engine and cooling system, reduces the risk of overheating, and enhances the overall efficiency of the cooling system.

This balanced mixture is particularly advantageous because it lowers the freezing point of the coolant to around -37 degrees Fahrenheit (-38 degrees Celsius) and raises the boiling point to over 265 degrees Fahrenheit (129 degrees Celsius) when under pressure. This makes it suitable for various climates and driving conditions, providing reliable engine performance year-round.

Alternatives like a 70/30 solution or a 100% EG composition may not provide the same level of protection. The concentrated antifreeze alone can lead to inadequate heat transfer, and while a higher concentration may offer better freeze protection, it compromises boiling point elevation and can potentially cause engine overheating.