Mercury 2002 Cougar Owner's Manual page 179

To maintain the integrity of the coolant and the cooling system and
maintain the warranty on the cooling system:
Add the type of coolant originally equipped in your vehicle. If
you are unsure which type of coolant your vehicle requires, check
your coolant reservoir or contact your local dealer.
Do not add/mix a green-colored coolant such as Motorcraft
Premium Engine Coolant, VC-4–A, meeting Ford specification
ESE—M97B44–A with the factory-filled coolant. Adding/mixing a
conventional green coolant can result in degraded corrosion
protection.
Do not add/mix a yellow-colored, extended life coolant such as
Motorcraft Premium Gold Engine Coolant, VC-7–A (or VC-7–B
in Oregon), meeting Ford specification WSS—M97B51–A1 with
the factory-filled coolant. Adding/mixing a yellow—colored
extended life coolant can result in degraded corrosion protection.
A large amount of water without engine coolant may be added, in case
of emergency, to reach a vehicle service location. In this instance, the
cooling system must be drained and refilled with a 50/50 mixture of
engine coolant and distilled water as soon as possible. Water alone
(without engine coolant) can cause engine damage from corrosion,
overheating or freezing.
Do not use alcohol, methanol or brine or any engine coolants
mixed with alcohol or methanol antifreeze (coolant). Alcohol
and other liquids can cause engine damage from overheating or
freezing.
Do not add extra inhibitors or additives to the coolant. These
can be harmful and compromise the corrosion protection of the engine
coolant.
Do not mix with recycled coolant unless from a Ford-approved
recycling process (see Use of Recycled Engine Coolant section).
For vehicles with overflow coolant systems with a non-pressurized cap
on the coolant recovery system, add coolant to the coolant recovery
reservoir when the engine is cool. Add the proper mixture of coolant and
water to the "cold full" level. For all other vehicles, which have a coolant
degas system with a pressurized cap, or if it is necessary to remove the
coolant pressure relief cap on the radiator of a vehicle with an overflow
system, follow these steps to add engine coolant.
Maintenance and Specifications
179