Pontiac 2007 G6 Owner's Manual page 326

When to Add Engine Oil
L4 Engine
V6 Engine
If the oil is below the cross-hatched area at the
tip of the dipstick, you will need to add at least
one quart/liter of oil. But you must use the right kind.
326
This section explains what kind of oil to use. For
engine oil crankcase capacity, see Capacities and
Specifications on page 424.
Notice: Do not add too much oil. If the engine
has so much oil that the oil level gets above the
upper mark 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. Push
the dipstick all the way back in when you are
through.
See Engine
Compartment Overview
on page 318 for the
location of the engine
oil fill cap.