The fuel-saving capabilities of various experimental and commercial passenger car engine oils have been demonstrated in extensive studies. Lower viscosity oils and those containing friction-reducing additives have shown measurable fuel economy benefits in a wide range of laboratory and vehicle tests. Several test techniques are described for screening fuel-saving engine oils and components. Closely controlled chassis rolls and over-the-road vehicle tests are utilized to demonstrate the actual lubricant-related fuel economy benefits.Within the range of variables included in this study, reducing engine oil viscosity is the most effective way to improve fuel economy. Fuel savings realized from friction-reducing additives are relatively modest and many of the more effective materials are shown to have poor performance in standard sequence tests, particularly regarding engine wear. The most appropriate fuel-saving engine oil should combine the benefits of low viscosity along with the use of a carefully selected and thoroughly tested friction-reducing additive.We strongly support industry efforts to standardize a test procedure for identifying fuel-saving engine oils. Based upon these studies and other investigations, the most suitable method for such a procedure are the EPA FTP and HWFET cycles.