Chevrolet TrailBlazer 2007 Owner's Manual page 518

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 404 for information on the Engine Oil Life
System and resetting the system.
When the change engine oil light or CHANGE
ENGINE OIL DIC 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 light
or 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 light
or message comes on 10 months or more since
the last service or if the light or message has
not come on at all for one year.