Cadillac 2010 STS Owner's Manual page 379

The engine air cleaner/filter is in the engine
compartment on the driver's side of the vehicle, near
the front. See
for more information on locating the air
cleaner/filter.
Inspect the air cleaner/filter at the Maintenance
intervals and replace it at the first oil change after each
80 000 km (50,000 mile) interval. See
for more information. If you
are driving in dusty/dirty conditions, inspect the filter at
each engine oil change.
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