Oil seals maintain seal performance while being compact due to a small seal width. Adopting a line contact lip with appropriate tension, the oil seal demonstrates high sealing performance in low torque zones without losing flexibility or eccentric-resistance. The rubber material has superior durability and achieves low heat generation and long life even at high velocity. Sealing performance and service life are dramatically improved due to a special spiral screw (hydro dynamic rib) mounted in either one direction or both.