A see-through plastic reservoir, similar to the familiar windshield washer reservoir, connects to the radiator by a hose. The engine coolant temperature rises with the vehicle operation. This causes the coolant to expand. The displaced coolant flows from the radiator to the recovery reservoir. When the engine stops, the coolant contracts as the coolant cools. This creates a vacuum which draws the displaced coolant back into the radiator. The radiator remains full of the coolant at all times. Keep the coolant level between the ADD and the FULL marks on the recovery reservoir. These marks are about one liter (one quart) apart. Use a 50/50 mixture of orange colored silicate free Dex-Cool® antifreeze and clean, drinkable water.