In designing fuel economy oils, two useful approaches are reduction of viscosity and incorporation of friction reducers. To achieve viscosity reduction without incurring problems of high oil consumption and possible interference with catalyst or oxygen sensor performance, the use of part-synthetic lubricants can be helpful. In this way, oil volatility (therefore oil consumption) is reduced and fuel economy is improved without incurring engine operating penalties. Friction reducers also can be used to improve fuel economy. The combination of these approaches furnishes the benefits of both. Laboratory and road testing of such combinations show important fuel economy benefits in normal vehicle operation, greater than those achievable from either approach alone. In addition, all other engine performance requirements are completely met. This advance in engine oil formulation technology, which opens up new possibilities to both vehicle manufacturers and consumers, is being further pursued.