In all honesty and I say this without jest it's the one marked "oil" good luck.
On the bottom.
the bottom
5.5 quarts
It depends on what climate you live in.
It is Attached to the oil filler cap
There is an oil cap in middle of forward valve cover, has a black cap with yellow markings.
5w-30 It says it right on the oil cap.
The heater core on the Chrysler LHS in behind the dash in the heater box. Unless you have the JDM version, then the heater core is in the oil pan next to the turbo.
On the oil cap it says "5 W 30".
next to the oil cap
To add oil to a 1996 Mercury Mystique, first locate the oil filler cap on the top of the engine, which is usually labeled with an oil can symbol. Unscrew the cap and use a funnel to pour in the appropriate type and amount of oil, as specified in the owner's manual. After adding oil, replace the cap securely and check the oil level with the dipstick to ensure it is within the recommended range.
Remove the cap on the valve cover and pour it in there.