Most aftermarket air filters like Pipercross or K&N will come pre-oiled from the factory, however, over time the air filter will get dirty and will need to be cleaned and reoiled. This handy video, complete with captions for those of you with no sound, shows you how to clean and oil your K&N air filter according to the manufacturer's instructions:
Link
How2 - Clean and oil your K&N Air Filter (Panel or Cone)
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