A copper passivator, corrosion and rust inhibitor of the film-forming type. It shows synergistic properties with various metal organic EP additives such as the dithiocarbamates. Used in petroleum fuels and solvents at 1 to 10 pounds per 1,000 barrels to prevent copper stain and corrosion. Used in petroleum base oils and greases and in synthetic base greases at 0.02 to 0.5% to protect copper. VANLUBE 601 has shown color stabilizing properties in oils and greases stored at elevated temperatures. It is a useful E.P. synergist with a variety of extreme pressure and antiwear additives.