Car Maintenance: Know Your Antifreeze

Antifreeze — a.k.a. Coolant — Keeps Your Engine in Top Shape

It's -20 degrees. Your car has been outside all day, yet it starts right away. Or, maybe it's 105 degrees and your car is purring along the highway, at no risk of overheating.

In each case, you can thank an engine additive that keeps your car's engine running smoothly.

Antifreeze and Coolant

Antifreeze, also known as coolant, is a bright yellow or green liquid that mixes with the water in cars, trucks and other vehicles to keep the radiators from freezing or overheating.

Made from either ethylene glycol or propylene glycol, antifreeze and coolant change the freezing and boiling points of water. For example, when mixed 50/50 with water in a car's radiator, water no longer freezes at 32 degrees Fahrenheit. Instead, water will freeze at temperatures colder than -35 degrees Fahrenheit. Likewise, while water alone will typically boil at 212 degrees Fahrenheit, antifreeze mixed with equal parts water won't boil until it reaches 223 degrees Fahrenheit.

Antifreeze Poisoning

Antifreeze made from ethylene glycol is a slightly sweet-smelling chemical that is toxic to pets, wild animals and humans, even in relatively small doses. For example, when it comes to ethylene glycol:

  • Two ounces can kill a dog.
  • One teaspoon can be lethal to a cat.
  • Two tablespoons can be hazardous to children.

When ethylene glycol is swallowed, it turns into acid that damages kidneys, causing kidney failure and even death.

Choosing Antifreeze or Coolant

If you have pets or young children in your household, you may be interested in a different type of antifreeze or coolant, made from propylene glycol. This type of antifreeze or coolant is toxic only when consumed in larger quantities. That makes it a good option for families with pets or children.

Checking Your Car's Antifreeze or Coolant Levels

Your car's manual will tell you how frequently you should check your antifreeze or coolant levels. If you have your oil changed by a mechanic, he or she may also check your antifreeze/coolant levels and top them off if necessary.

If you change your own oil, or you want to check your antifreeze or coolant condition and levels, look for the overflow reservoir in the engine compartment. (Check your owner's manual for the exact location of your overflow reservoir.) Use a hydrometer to verify the condition of the coolant. The device will tell you the minimum and maximum temperatures the antifreeze or coolant will work. You'll also be able to see your antifreeze or coolant levels. Be sure the levels meet the guidelines in your car's manual.

Antifreeze or Coolant Disposal

Because both ethylene glycol and propylene glycol are dangerous chemicals, many states have outlined specific procedures for disposing of used antifreeze or coolant. Never dump antifreeze or coolant down the drain or on the ground. Antifreeze will pollute rivers and streams or seep through the ground into the groundwater. Instead, store antifreeze in a clearly labeled container and drop it off at an antifreeze recycler. Recyclers can reuse, distill or filter antifreeze, removing hazardous contaminants and readying it for re-use.

Knowing your antifreeze or coolant, checking it regularly and disposing of it properly are not only good for your car, they're also good ways to keep your family members and pets safe at home.