The present invention relates to a novel use of nanomaterials as a viscosity modifier and thermal conductivity improver for gear oil and other lubricating oil compositions. The gear oils of the instant invention have a higher viscosity index, higher shear stability, and improved thermal conductivity compared to currently available gear oils. The preferred nanoparticles also impart a reduction in the coefficient of friction, including reduced friction in the boundary lubrication regime. These properties are obtained by replacing part or all of the polymer thickener or viscosity index improver or some other part of the composition normally used in gear oils with nanomaterials of suitable shape, size, and composition.