It does the same thing a filter in your home heating/AC unit does. Filters out junk in the air. Alot of vehicles dont even have them. some have the slot but wont put the filter in.
NAXJA Member #2619
1995 Jeep Sport Cherokee 4x4 with an Auto and 4.0L
B&M Transmission Cooler and Autometer Tranny Temp Gauge, Ruff Stuff Diff Cover on D30.
Taraflex 1.5" BB (rear shackle only), HD Quadratec leaf springs, RE 3.5" front springs, OME Long shocks, JKS Adjustable Track Bar from K.O.R.
Daystar Control Arm Bushings, Bushwhacker Flairs, Rhino lining along bottom trim, AGR PS pump with Cooler & Filter.
Bored TB, APN Manifold, New Downpipe, Magnaflow High Flow Cat, Flowmaster Super 44.
Dual Oil Relocation Kit running two K&N301 size filters, Autometer Digital Cobalt Oil Temp and Oil Pressure Gauge.