Lexus GS300 1998 Owner's Manual page 220

20G009
2. Take out the air filter.
If it is dirty, it should be replaced. To maintain the air
conditioning efficiency, replace the air filter according to the
maintenance schedule. (For scheduled maintenance
information, please refer to the separate "Owner's Manual
Supplement/Maintenance Schedule".)
NOTICE
Do not drive with the air filter removed, or the efficiency
of air conditioning may be lost.
AIR CONDITIONING AND AUDIO
207