Antifreeze keeps the cooling system from freezing, which in turn protects the engine from overheating. Many seasonal regions have been experiencing mild winters this year, but it's still important to keep a watchful eye on the coolant all winter long.
Antifreeze needs to be mixed with water in your car's cooling system so the water does not freeze. Water alone can cool an engine, but when temperatures drop, it can freeze, which is why a chemical mixture is added. Coolant's main component, ethylene glycol, prevents the water in the radiator and engine from freezing in cold temperatures, and it helps to protect against boiling waters in the summer.
For climates that don't have especially harsh winters, the general rule of thumb is to mix even parts water and antifreeze. However, the ratio may be tipped in the coolant's direction. Adding more coolant that water can lower the mixture's freezing point even further than the standard combination. The owner's manual will be able to guide you to the proper ratio for your location.
The coolant is also used to reduce the corrosion within the cooling system. In addition to the ethylene glycol, there are other additives combined with the antifreeze to prevent rust and damage to the parts it comes in contact with. This also lubricates the water pump and any seals along the way.
There are different types of antifreeze, most commonly denoted by their coloration. Typically, coolant will be either green or orange. Toyota uses a red coloration for their antifreeze, but other than the color, it is the same as the green kind. Greed (and red) coolant uses alkaline materials such as silicates, phosphates and borates to reduce corrosion and keep the solution from becoming acidic. After a while, these inhibitors will no longer be effective, and if you wait too long to change the solution, you could risk damaging your car.
Orange antifreeze relies on organic acids to prevent corrosion. These inhibitors typically last much longer than those found in green coolant. Since one uses acids and the other uses alkalines, it is important not to mix them together, as this can increase the risk of corrosion. If you want to switch from one to the other, you will need to fully flush the system beforehand. Some older cars will not be able to use the orange coolant, and an automotive professional will be able to help you determine whether it's safe to make the switch in your particular model.