Auto Talk: All about coolant

All car engines have some type of cooling system. Most use a liquid coolant that circulates around the engine to carry heat away. How does coolant work and what do you need to know about it?

Coolant is a mixture of water and various chemicals. The chemicals help prevent rust, neutralize acids and lubricate moving parts such as the water pump. They also increase the boiling point and lower the freezing point of the water. Many people refer to coolant as antifreeze—this is an outdated term, as protection against freezing is just one of many tasks the coolant handles.

There are four main types of coolant available. Contrary to popular belief, you can’t tell them apart by color. Coolant manufacturers can make their products any color they like.

  • Standard coolant is made of ethylene glycol. It lasts about two years or 30,000 miles.
  • Dex-Cool is a blend of ethylene glycol and various polymers. It lasts about five years or 150,000 miles, but the catch is that it needs to be used from the day the car rolls off the assembly line. When added to a car that has previously used other types of coolant, Dex-Cool has the same lifespan as standard coolant.
  • Environmentally friendly coolant is made of propylene glycol, which is less harmful to the environment than ethylene glycol. It doesn’t mix with other coolants, so the system must be completely drained before switching to this type.
  • Recycled coolant is any type of used coolant that has been drained from other vehicles, filtered, and had any lost additives replaced. It often costs less than new coolant.

Check your owner’s manual to see if the car came with Dex-Cool originally. If so, stick with it. If not, simply choose a coolant based on price or other factors that are important to you. Standard, recycled and environmentally friendly coolants will all work the same in your vehicle.

For the cooling system to work properly, the coolant must be full, and it must have the correct concentration and pH level. The first is easy to check. The small plastic overflow tank near your car’s radiator will have two lines on it. When the engine is cold, the coolant level should be between these two lines. If it’s too low, add some coolant, pre-mixed with the amount of water specified on the label.

The concentration and pH level can be estimated with a paper test strip, available at auto parts stores. (A truly accurate test can be done by your auto technician, using a refractometer.) If the pH isn’t balanced but the coolant is still good in other ways, adding a bottle of anti-rust will bring things back to normal and extend the life of your coolant.







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