In rotating equipment—from electric motors and pumps to gearboxes and conveyors—protecting bearings from contamination and preventing lubricant leakage are critical to reliability and service life. For decades, oil seals (radial shaft seals) have been the standard solution for this task. More recently, bearing isolators have gained popularity as a non-contact, long-life alternative. While both serve the same fundamental purpose, they work on entirely different principles and are suited to different operating conditions. This article compares oil seals and bearing isolators, explains how each works, and provides guidance on selecting the right protection for your application.