Cadillac 2008 CTS - Manual (Page 299)

When to Add Engine Oil
If the oil level is within the add 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 5-128.
Notice: Do not add too much oil. If the engine
has so much oil that the oil level gets above the
proper operating range and into the upper
cross-hatched area on the dipstick, 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. Push the dipstick all
the way back in when you are through.
5-17