Results of the development of new methods for the investigation and evaluation of the properties of lubricants with various additives are discussed. The use of an electrokinetic investigation method combined with a radiotracer method has permitted studying the mechanism of the detergent action of some additives for motor oils in the presence of an electric field. It is shown that the simultaneous evaluation of the antiwear and detergent properties of motor oils is possible with additives and a laboratory radiotracer method. A radiotracer method is suggested for studying the chemical activity of EP additives for motor oils at temperatures from 200 to 600 C in the zone of the contact of the metal surface with the oil.Presented as an American Society of Lubrication Engineers paper at the Lubrication Conference held in Washington, D.C., October 13–16, 1964