How much oil does a 1996 grand am need?
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.
There is actually a pump underneath the crankshaft inside the engine that pumps the oil over the moving parts. This pump may need replacing depending on the milage. This is a costly task, and luckily with a 1996 is also unlikley. The more likely cause of the problem could be a faulty sensor (known as the oil pressure sender unit) inside the oil pan.