Which type of coolant is not poisonous?

• A. Ethylene glycol based
• B. Propylene glycol based
• C. Alcohol based
• D. Water only

Answer: (B)

The important point is safety and toxicity differences among common coolant chemistries. Ethylene glycol–based coolant is highly poisonous if ingested and is a major health hazard to people and pets. Alcohol-based coolant also poses health risks and is flammable. Water by itself isn’t a practical coolant because it lacks the additives that prevent freezing, boiling, and corrosion inside the engine, so it isn’t used as a stand-alone coolant. Propylene glycol–based coolant is designed to be much less toxic than ethylene glycol, offering a safer profile while still providing the necessary protection for the cooling system. That combination of reduced toxicity and effective cooling protection makes it the best choice in this context.