Cadillac 2007 CTS Owner's Manual page 349

You should look for this on the oil container, and
use only those oils that are identified as meeting
GM Standard GM4718M and have the starburst
symbol on the front of the oil container.
Your vehicle's engine is filled at the factory
®
with a Mobil 1 synthetic oil, which meets all
requirements for your vehicle.
Oils meeting these
requirements should
also have the starburst
symbol on the
container. This symbol
indicates that the oil
has been certified by the
American Petroleum
Institute (API).
Substitute Engine Oil: When adding oil to maintain
engine oil level, oil meeting GM Standard
GM4718M may not be available. You can add
substitute oil designated SAE 5W-30 with
the starburst symbol at all temperatures. Substitute
oil not meeting GM Standard GM4718M should
not be used for an oil change.
Engine Oil Additives
Do not add anything to the oil. The recommended
oils with the starburst symbol that meet GM
standards are all you will need for good
performance and engine protection.
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