I bought a used '96 SSe 6 weeks ago I had an interesting experience with adding oil...I put in about 1/2 a quart OVER and subsequently on the highway Bonne began to hesitate and sputter a bit if I pressed the gas anything but gradually. This was only happening at 50mph and over.
So I took Bonne to Wally World and had them change her oil. I watched the Wal-Mart people like a hawk because they are inept; I counted the oil being put in after the change and said "stop!" right at the 4 1/2 quart mark.
Bonne was fine again after this. I never had a car before that was sensitive to oil overfill.
On the receipt from Wal-Mart it says, "Pre Service Oil Check - CHECKED, Half Quart Low"
Beware of Wal-Mart gotta watch everything they do!