Chevrolet 2003 Impala Owner's Manual page 363

Engine Oil Scheduled Maintenance
Change engine oil and filter as indicated by the GM
Oil Life SystemTM (or every 12 months, whichever
occurs first). Reset the system.
Your vehicle has a computer system that lets you know
when to change the engine oil and filter. This is
based on engine revolutions and engine temperature,
and not on mileage. Based on driving conditions,
the mileage at which an oil change will be indicated can
vary considerably. For the oil life system to work
properly, you must reset the system every time the oil is
changed.
When the system has calculated that oil life has been
diminished, it will indicate that an oil change is
necessary. A CHANGE ENGINE OIL message will
come on. Change your oil as soon as possible within
the next two times you stop for fuel. It is possible that, if
you are driving under the best conditions, the oil life
system may not indicate that an oil change is necessary
for over a year. However, your engine oil and filter
must be changed at least once a year and at this time
the system must be reset. It is also important to
check your oil regularly and keep it at the proper level.
If the system is ever reset accidentally, you must
change your oil at 3,000 miles (5 000 km) since your
last oil change. Remember to reset the oil life system
whenever the oil is changed. See
Engine
Oil on
page
5-15 for information on resetting the system.
After the services are performed, record the date,
odometer reading and who performed the service on the
maintenance record pages in Part E of this schedule.
An
Emission
Control
Service
6-6