well you wouldn't expect it to be clean would you? as long as the brown stuff isn't on the top side you needn't fret. this is what filters do, stop the dust getting into your engine. the filter is impregnated with oil to catch the dust, whereupon it starts to resemble brown slime. et voila!Just went to clean it to find it with sticky brown stuff on the bottom side and in the bottom of the air box .