A comprehensive study of urea greases obtained on the basis of Group I distillate oils, which have a viscosity in the range from 24.4 to 342.0 mm(2)/s at 40 degrees C, has been carried out. The results obtained have made it possible to reveal the dependence of various physicochemical parameters of greases (dropping point, ultimate strength, colloidal stability, wear rate) on the viscosity of the base oil and the structure of diurea used as a thickener. The revealed relations allow prediction of the properties of greases at the stage of selecting the initial components.