Final answer:
Ethylene glycol is not an excellent coolant when used alone; it is typically mixed with water to better regulate engine temperatures and because pure ethylene glycol does not transfer heat as effectively. Therefore, the statement "Ethylene glycol is an excellent coolant when used alone" is False.
Step-by-step explanation:
Ethylene glycol is also toxic, particularly to household pets who may ingest it due to vehicle antifreeze leaks. Because of this, although it is effective in preventing the formation of ice, care should be taken to handle and dispose of it appropriately. Its toxicity also has given rise to alternatives like propylene glycol, which is less harmful. Therefore, the statement "Ethylene glycol is an excellent coolant when used alone" is False.