The invention provides an open gear lubricant composition containing a blend of ethylene-propylene copolymers and a metallic soap thickener. The blend of ethylene-propylene copolymers includes a first ethylene-propylene copolymer having a kinematic viscosity at 100 C. of 80 centistokes to 220 centistokes and a second ethylene-propylene copolymer having a kinematic viscosity at 100 C. 500 centistokes to 3000 centistokes. The invention further relates to a method of lubricating a mechanical device with the open gear lubricant composition.