Pontiac G5 Owner's Manual page 376

When the CHANGE OIL SOON 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 OIL SOON 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
CHANGE OIL SOON message comes on
10 months or more since the last service or if the
message has not come on at all for one year.