What viscosity of oil is recommended for the Mercury Cougar V6 engine?

The recommended oil viscosity for a Mercury Cougar V6 engine depends on the specific year and engine. There's no single answer. The owner's manual for your particular Cougar will specify the recommended viscosity grades (e.g., 5W-30, 10W-30, etc.) and the type of oil (conventional, synthetic, etc.).

To find the correct information, you need to:

1. Locate your owner's manual: This is the definitive source.

2. Identify the engine: The engine displacement (e.g., 3.0L, 3.8L) will be listed in the manual or on an engine sticker.

Without knowing the year and specific engine of your Mercury Cougar, I cannot provide a correct oil viscosity recommendation. Using the incorrect viscosity could damage your engine.