This paper examines the various factors controlling the effect of lubricants on fuel economy. The main mechanisms that contribute to energy losses in a lubricant/machine system are discussed, and examples of the contributions of the corresponding parameters are given. Synergistic combinations of the principal energy-saving components are noted and applied, with an emphasis on engine oil formulations. It is concluded that the optimum 5W-30 formulation combines a base reinforced with a polyaphaolefin oligomer and a friction-modified additive package. This combination also would help solve other industry problems, such as low-temperature engine failures and excess wear and blowby situations at high temperatures.