Development of Engine Test Method to Discriminate Engine Oils and Additives in Terms of Motoring Torque

Improvement in fuel economy and reduction in emissions are the two major driving forces in the advancement of automotive engine technologies, fuel quality, lubricants, and aftertreatment devices. Engine design, operating conditions such as speed and load, and engine oil behavior have a significant influence on engine friction and then the vehicle fuel economy. There is no standard short duration engine test available to evaluate engine oil’s friction. This study developed a test protocol to discriminate friction reduction efficacy of engine oils/additives to support in the development of engine oils. The engine test facility was modified to conduct the motoring test over the speed range of 1000 - 4500 rpm and at 50 - 100 °C coolant and oil temperatures. Different viscosity grades and additive chemistry i.e. combination of friction modifiers & viscosity modifiers was evaluated over the motored torque test. Repeatability of test results was also ensured by conducting the test many times under the same temperature/speed conditions. High viscosity index engine oils have shown better performance compared to low viscosity index oils at all the temperature conditions. Low viscosity engine oils reduced frictional losses and it is established that improvement in the fuel economy of the engine over the transient test cycle while using low viscosity engine oils. The friction reduction performance of same grade engine oils mainly depends upon the synergy of different constituents of an additive package. This motoring torque test method has shown its capability to discriminate engine oils of different viscometrices & friction modifiers and this can be used as an excellent screening tool to assess friction reduction potential of engine oils.