Chevrolet Optra 2005 Owner's Manual page 216

To inspect or replace the filter, do the following:
1. Remove the four screws that hold the cover on.
2. Lift off the cover.
3. Inspect or replace the engine air cleaner/filter.
See Normal Maintenance Replacement Parts
on page 5-83 for replacement part numbers.
4. Put the cover back on tightly and tighten
the screws.
See Using Your Maintenance Schedule on page 6-4 for
replacement intervals.
5-18
CAUTION:
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Operating the engine with the air cleaner/filter
off can cause you or others to be burned. The
air cleaner not only cleans the air; it helps to
stop flame if the engine backfires. If it is not
there and the engine backfires, you could
be burned. Do not drive with it off, and be
careful working on the engine with the air
cleaner/filter off.
Notice: If the air cleaner/filter is off, a backfire can
cause a damaging engine fire. And, dirt can
easily get into your engine, which will damage it.
Always have the air cleaner/filter in place when you
are driving.