The testing technique outlined in this recommended practice was developed as part of an overall program for testing and evaluating fuel consumption of heavy-duty trucks and buses. The technique outlined in this recommended practice provides a general description of the type of equipment and facility which is necessary to determine the power consumption of these engine-driven components. It is recommended that the specific operating condition suggested throughout the test be carefully reviewed on the basis of actual data obtained on the specific vehicle operation. This recommended practice covers evaluation techniques for determining the power consumption characteristics of hydraulic pumps used on heavy-duty trucks and buses.