If it's a 3.8L then there is your answer, 3.8 liters of oil. If it's a 3.3L, use 3.3L of oil.
According to the 1996 Mercury Grand Marquis owners manual ( 5W-30 engine oil ) is the PREFERRED oil weight
In the oil pan
Try about 3.5L
You should add 4.5 liters of oil when changing the oil and the oil filter.
According to the 1996 Mercury Grand Marquis Owner Guide ( 5W-30 is the PREFERRED engine oil )
On the side or bottom of the oil pan.
According to the 1996 Mercury Grand Marquis Owner Guide : ( 5W-30 is the PREFERRED engine oil weight )
Try changing you oil and if that does not help you will need to rebuild the tranny or replace it.
On the oil pan.
It's around 4ltr.
5 Qts. I suggest 10W-40
According to the 1996 Mercury Grand Marquis Owner Guide : With engine oil filter change : ( 5 quarts / 4.7 liters of engine oil ) * the engine oil dipstick is used to determine the exact fill requirement *