Which oil do you use for a 99 merc cougar v6?

The recommended oil for a 1999 Mercury Cougar V6 depends on the specific engine and the climate where you live. Consult your owner's manual for the most accurate recommendation. However, generally speaking, a 1999 Cougar V6 (likely a 2.5L Duratec or a 3.0L Vulcan) would typically use:

* 5W-20: This is a common recommendation for modern engines and often preferred for fuel economy and cold-weather starting. Check your owner's manual to be sure.

* 5W-30: This is a slightly thicker oil, often suitable for hotter climates or higher mileage engines. Again, your owner's manual is the final authority.

Crucially, always check your owner's manual. It will specify the exact type and weight of oil recommended by the manufacturer for your specific engine. Using the wrong oil can damage your engine.