Your new neighbors are right! It might seem counterintuitive, but despite the name, antifreeze can freeze. This typically happens at around -5 degrees Fahrenheit.
But keep in mind that what you’re putting in your car isn’t actually pure antifreeze—it’s coolant. Coolant is a combination of antifreeze and water, typically as a 50/50 mixture.
As strange as it sounds, adding the water to antifreeze actually lowers the freezing point. That’s why coolants are sold as different ratios of antifreeze to water, with different freezing points:
100/0 (pure antifreeze: Freezes at 0 to -5 degrees Fahrenheit
50/50 (standard coolant): Freezes at -35 degrees Fahrenheit
70/30 (cold-climate coolant): Freezes at -67 degrees Fahrenheit
For harsh winter climates, 70/30 coolants are recommended.
MORE: Antifreeze vs. coolant