2005 Pontiac GTO Owner's Manual - Page 200

When to Add Engine Oil See Engine Compartment Overview on page 5-12 for the location of the engine oil fill cap. If the oil is at or below the cross-hatched area at the tip of the dipstick, then you will need to add at least one quart of oil. But you must use the right kind. This section explains what kind of oil to use. For engine oil crankcase capacity, see Capacities and Specifications on page 5-90. Notice: Do not add too much oil. If the engine has so much oil that the oil level gets above the cross-hatched area that shows the proper operating range, the engine could be damaged. Be sure to add enough oil to put the level somewhere in the proper operating range in the cross-hatched area. Push the dipstick all the way back in when you are through. 5-14