"We would like to standardize on one brand of oil for all our gearboxes, but our worm gear manufacturer tells us we shouldn't use the extreme pressure (EP) gear oil we use for our reduction gears for this application. Why can't you use EP oil for worm gears?"

Many EP gear oils contain sulfurous additives. These additives are designed to chemically bond to the metal surface of the gears and other components under boundary lubrication conditions to prevent welding of asperities on the two opposing surfaces. 

While vital in preventing metal-to-metal contact in boundary lubrication regimes, they can be corrosive under certain conditions, particularly to yellow metals such as copper, brass and bronze, which are commonly used in industrial worm gears and other components.

The best approach to selecting the correct product for a given application is to gain a thorough understanding of the gear type, metallurgy and operating conditions of the component and to discuss these points with your lubricant supplier and equipment manufacturer. The correct lubricant can then be selected based on load, speed, operating temperature and additive requirements.