Antifreeze/ engine coolant maintenance is one of the basic engine care tasks that most car owners can handle by themselves. It is more complicated, however, than just topping off the coolant overflow reservoir with water when it runs low.
We've all seen cars sitting by the side of the road, hood open, with steam billowing out from the engine. This means that the car has overheated and the engine coolant is boiling away. Continuing to operate a vehicle that is overheating or in which the there is insufficient coolant left in the system can result in many thousands of dollars of damage to your engine, including break-down of your engine oil viscosity, bent piston rods, cracked heads, and even melting plastic components inside the engine compartment.
Every new car service plan includes periodic checking and maintaining of important engine fluids like anti-freeze, but for older cars or car owners who may not, for one reason or another, always make it to regularly scheduled service checks, engine coolant maintenance is an important part of keeping your car in tip-top shape. Engine coolant keeps your engine from overheating, but also helps distribute heat throughout the engine in extremely cold weather. The chemical properties of properly mixed engine coolant will also help prevent corrosion inside the cooling system, extending the life of the radiator and coolant lines.
Your owner's guide will tell you what kind of engine coolant mix your vehicle needs. Often it will be a 50-50 mix of anti-freeze and water. If this is the case, then it is likely that the owner's guide will also warn you against adding some of the new "high-tech" improved types of anti-freeze. You should never mix the two different kinds of anti-freeze. Cars are designed for certain types of anti-freeze and adding the wrong formulation can nullify the anti-corrosive properties of the anti-freeze for which your car's coolant system was designed, reducing the lifespan of your radiator dramatically.
If you just add water every time your engine coolant needs to be topped off, you'll be diluting your coolant and making it less effective not only at corrosion resistance, but also in its primary task of keeping your engine within operational temperature limits. Similarly, if you simply add more anti-freeze, you'll be increasing the concentration of the coolant beyond your car's design.
To make sure you add water and anti-freeze in the right mix, you can buy an inexpensive anti-freeze tester. By following directions that come with the tester when your engine coolant is running low, you can determine if the remaining coolant in your engine deviates from the 50-50 mix that your owner's manual calls for. If it does, then you can add either more anti-freeze or more water to get it back to the right mix and level.
Of course, if you bring your car in to your dealer's service station for regular servicing, they'll take care of everything for you and make sure that your engine fluids are kept at optimum levels.