All automotive gear oils must satisfy a series of standard industry or Original Equipment Manufacturer (OEM) tests. These usually include bench, axle dynamometer, and field tests. However, product development testing must extend beyond satisfying standard test protocols. This is especially true as increased emphasis is placed on extending oil drain intervals and increasing equipment life in the face of greater performance demands through new heavy-duty vehicle designs.End-users ultimately benefit from extended oil drain intervals and increased equipment life. However, the effort to achieve both initiatives will prove successful only through careful development and selection of the proper performance additives and base fluids. Also, a broad focus must be maintained to satisfy all lubricant requirements. These requirements build on a solid base of standard features and include new features that stretch the current envelope of gear oil performance.This paper highlights new automotive gear oil technology specifically developed to balance the opposing needs of extended oil drain intervals and extended equipment life in heavy-duty trucks and buses.