Ford Mercury Villager 1997 Owner's Manual page 290

Adding Engine Coolant
Engine coolant recovery reservoir
Do not put engine coolant in the container for the
windshield washer fluid.
When the engine is cool, add a 50/50 mixture of engine coolant
and water to the engine coolant recovery reservoir — DO
NOT ADD DIRECTLY TO THE RADIATOR. Add straight water
only in an emergency, but you should replace it with a 50/50
mixture of coolant and distilled water as soon as possible.
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WARNING