Cadillac 2011 CTS Coupe Owner's Manual page 334

Selecting the right engine oil
depends on both the proper oil
specification and viscosity grade:
Use and ask for engine oils with
the dexos certification mark. Oils
meeting the requirements of the
vehicle should have the dexos
certification mark on the container.
This certification mark indicates that
the oil has been approved to the
dexos specification.
This vehicle was filled at the factory
with dexos approved engine oil.
Use of Substitute Engine Oils if
dexos is unavailable: In the event
that dexos approved engine oil is
not available at an oil change or for
maintaining proper oil level, you
may use substitute engine oil
displaying the API Starburst symbol
and of SAE 5W-30 viscosity grade.
Use of oils that do not meet the
dexos specification, however, may
result in reduced performance under
certain circumstances.
SAE 5W-30 is the best viscosity
grade for the vehicle. Do not
use other viscosity oils such as
SAE 10W 30, 10W 40, or 20W-50.