The heater core allows hot air inside your car in the winter and the radiator keeps the engine cool at all times. 

Both of these systems utilize permanent coolant / antifreeze to operate correctly.  If the permanent coolant / antifreeze gets dirty and turns to sludge it can plug up the heater core causing loss of heat.  If the antifreeze becomes too weak it can no longer prevent corrosion from building up inside the radiator, it can lose its ability to lubricate the water pump properly and may no longer prevents ice from forming in the radiator or engine block.  The two types of antifreeze are green coolant (ethylene glycol) and the ELC coolant (extended life coolant) which can vary in color from yellowish to an orange red color depending on the manufacturer.  Green coolant uses inorganic materials where as the ELC coolant uses an organic acid technology. ELC coolant will on the average last 2 1/2 times longer than the conventional green coolant and does a better job of protecting against corrosion as long as it has not been contaminated or over diluted.  Making sure that the engine coolant is clean and at the correct strength will insure a warm winter for you and a longer life for your engine. Utilizing deionized water will also extend the life of the coolant and help keep harmful mineral deposits from forming in your cooling system. Rad Air utilizes deionized water in all cooling systems.