Cadillac 2007 CTS Owner's Manual page 464

If the engine oil life system is ever reset
accidentally, you must service your vehicle within
3,000 miles (5 000 km) since your last service.
Remember to reset the oil life system whenever
the oil is changed. See Engine Oil Life System on
page 350 for information on the Engine Oil Life
System and resetting the system.
When the Change Engine Oil message appears,
certain services, checks, and inspections are
required. Required services are described in the
following for "Maintenance I" and "Maintenance II."
Generally, it is recommended that your first
service be Maintenance I, your second service
be Maintenance II, and that you alternate
Maintenance I and Maintenance II thereafter.
However, in some cases, Maintenance II may be
required more often.
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Maintenance I — Use Maintenance I if the
change engine oil message comes on within
10 months since the vehicle was purchased or
Maintenance II was performed.
Maintenance II — Use Maintenance II if the
previous service performed was Maintenance I.
Always use Maintenance II whenever the message
comes on 10 months or more since the last
service or if the message has not come on at all
for one year.