Pre-Oiled Air Filter. Twin Air Factory Pre-Oiled filters have been available only to top professional race teams and O.E.M. customers. The results have been so good that Twin Air now offers the same factory treatment to everybody. They start with an Original Dual-Stage Air Filter and completely submerge it in BIO Liquid Power Filter Oil. After the filter is massaged to ensure all pores are evenly coated with oil, it's placed in a temperature-controlled room to allow the oil to completely cure. You just open the re-sealable bag and install. The original Dual-Stage Air Filter completely coated in Twin Air's BIO Liquid Power Filter Oil. Twin Air filters are designed to increase airflow while ensuring the highest level of protection from dirt / dust. Coarse open-pore foam catches airborne dirt, grime and sand.