Antifreeze (coolant) also has additive packages to clean, lubricate the water pump, and keep seals soft. This procedure uses a chemical flushing agent to loosen debris from within the cooling system(including the heater core). The system is hooked up to a coolant recovery/recycle machine which filters the harmful contaminates from the antifreeze. The additive packages are replenished as the last step of the process, this also eliminates electro-chemical damage which is the primary cause of most coolant hose failures. The recommended service intervals are: 24,000 miles-city and 36,000 miles-highway.