Automotive cooling systems — commonly used antifreeze In passenger-car and light-commercial vehicle engines, which fluid is most commonly used as the antifreeze (mixed with water) for freeze protection, boil-over margin, and corrosion inhibition?

Introduction / Context:
Modern liquid-cooled automotive engines rely on a water-based coolant that includes an antifreeze component. The antifreeze lowers the freezing point, raises the boiling point, and carries a package of corrosion inhibitors that protect aluminum, cast iron, solder, and polymer components. Knowing the commonly used antifreeze is essential for correct service and for avoiding chemical damage to the cooling system.

Given Data / Assumptions:

• Typical road vehicle with a pressurized cooling system and radiator.
• Coolant is a mixture of water and antifreeze concentrate.
• Goal: pick the industry-standard antifreeze base fluid.

Concept / Approach:
Across global markets, the dominant antifreeze base is ethylene glycol. It provides strong freezing-point depression and boiling-point elevation when mixed 40–60% with water. It also dissolves additive packages that inhibit corrosion and cavitation. Alternative chemicals listed in the options are either unsuitable or unsafe for this service.

Step-by-Step Solution:
Identify the required properties: freeze protection, boil-over protection, and corrosion inhibition carrier.Match those properties to candidates. Ethylene glycol meets all three when combined with inhibitor packages.Eliminate chemicals that are refrigerants, reactive salts, or toxic solvents with wrong physical properties for coolant duty.

Verification / Alternative check:
Owner manuals and service labels typically specify ethylene glycol based coolant. Some applications use propylene glycol as a less toxic alternative, but ethylene glycol remains the most common in OEM fills and aftermarket service worldwide.

Why Other Options Are Wrong:
Carbon disulphide is a volatile, highly flammable solvent, not a coolant base. Ammonium chloride is an ionic salt that would aggressively corrode metals. Freon-12 is a refrigerant used in legacy air conditioning systems, not in engine coolant circuits.

Common Pitfalls:
Mixing incompatible coolant chemistries, topping up with hard water that increases scale, and assuming color always denotes chemistry (it does not). Always follow OEM inhibitor technology requirements.

Final Answer:
ethylene glycol