Buick Century 2003 Owner's Manual page 215

What Kind of Engine Oil to Use
Oils recommended for your vehicle can be identified by
looking for the starburst symbol.
This symbol indicates that the oil has been certified by
the American Petroleum Institute (API). Do not use
any oil which does not carry this starburst symbol.
You should also use the proper viscosity oil for your
vehicle, as shown in the viscosity chart.
If you choose to perform
the engine oil change
service yourself, be sure
the oil you use has the
starburst symbol on the
front of the oil container. If
you have your oil changed
for you, be sure the oil put
into your engine is
American Petroleum
Institute certified for
gasoline engines.
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