GMC 2008 Acadia - Manual (Page 330)

When to Add Engine Oil
If the oil is below the cross-hatched area at the tip of
the dipstick, add at least one quart/liter of the
recommended oil. This section explains what kind of oil
to use. For engine oil crankcase capacity, see
Capacities and Specifications on page 5-107.
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.
See Engine Compartment
Overview on page 5-14 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 in the cross-hatched area.
Push the dipstick all the way back in when you are
through.
5-16