Pontiac 2006 G6 - Manual (Page 286)

When to Add Engine Oil
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. This section
explains what kind of oil to use. For engine oil crankcase
capacity, see Capacities and Specifications on
page 5-105.
Notice: Do not add too much oil. If your engine has
so much oil that the oil level gets above the upper
mark that shows the proper operating range,
your engine could be damaged.
See Engine Compartment
Overview on page 5-12 for
the location of the
engine oil fill cap.
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.
L4 Engine
V6 Engine
5-18