Pontiac 1997 Bonneville Owner's Manual page 268

When to Add Oil
If the oil is at or below the ADD mark, then you'll need
to add at least one quart of oil. But you must use the
right kind. This part explains what lund of oil to use. For
crankcase capacity, see "Capacities and Specifications"
in the Index.
What Kind of 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.
NOTICE:
Don't add too much oil. If your engine has
so much oil that the oil level gets above the
cross-hatched area that shows the proper
operating range, your engine could be damaged.
The engine oil fill cap is behind the engine oil dipstick
and engine fans.
Be sure to fill it enough to put the level somewhere in
the
proper operating range. Push the dipstick all the way
back in when you're through.
If you change your own oil,
be sure you use oil that 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
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I
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gasoline engines.
You should also use the proper viscosity oil for your
vehicle, as shown in the following chart:
6-15