Abstract: A nonclogging rotary disk filter is disclosed. The invention has relief holes provided in rotatable disks such that oil, other liquids, and gases may be separated from a liquid while the disks are rotated at high speeds. The relief holes are located close to the rotatable shaft supporting the disks. When the disks are rotated at high speeds, lighter liquids, oil, and gas bubbles tend to migrate to the area near the shaft which has relatively low centrifugal forces. In a gravitational field, the relief holes allow the lighter liquids, oil, and gas bubbles to migrate upwardly through the disks for removal. The disks are rotated fast enough to establish a barrier layer in a liquid over a working area of the disk surface having a surface velocity greater than 15 feet per second.