In the previous paper, the authors investigated the effects of viscosity of the base oil of cutting oil for hobbing on the synergism of EP additive and rape-seed oil. It was revealed that a mixture of 1% chlorine in the form of chlorinated fatty acid ester and 30% rape-seed oil added to a machine oil 68 with high viscosity showed the best performance in terms of reducing hob wear and improving finished surface roughness. The effects of viscosity of the base oil on the synergism of several kinds of additives were investigated in this work. Experiments were carried out using a single fly tool. A mixture of 0.5% sulfur in the form of sulfurized fatty oil and 1% chlorine in the form of chlorinated fatty acid ester added to a machine oil 32 with medium viscosity is optimal for practical applications.