Four engine lubricants were evaluated against a reference oil for fuel economy, exhaust emissions, horsepower output, oil consumption, and lubricating properties. Sixty 1977–79 automobiles were used for the evaluation, with each auto accumulating approximately 18,000 miles (28,980 KM). Fuel economy was measured by recording odometer readings and gallons used at each fill-up, and laboratory testing (Federal Test Procedure and Highway Fuel Economy Test) provided two other measures of fuel economy as well as exhaust emissions. Dynamometer horsepower tests were performed and the lubricating properties of each oil were determined by analyzing oil samples taken from the test vehicles at regular intervals. Major findings were: (1) On-the-road testing revealed that a low viscosity oil produced a fuel economy increase of 3.0%, a fluid friction modified oil produced a fuel economy increase of 2.7%; the remaining test oils did not produce any significant changes in fuel economy. (2) Laboratory testing revealed that the low viscosity oil produced a fuel economy improvement of 5.9%, one fluid friction modified oil produced a fuel economy increase averaging 5.6%; a solid-friction modified oil produced a fuel economy increase of 8.3%; the other fluid friction modified oil did not produce any significant fuel economy changes. (3) Testing for oil economy and lubricant properties also indicated no significant deterioration or differences among the oils.