Modern agriculture has evolved dramatically over the past half century. To be profitable, farms need to significantly increase their crop yields, and thus there are amplified demands on farming equipment. Equipment duty cycles have been raised in scope and duration, as the required output of the agricultural industry to sustain a growing population has stimulated the need for further advances in effective productivity gains on the farm. The mainstay mechanical assistant to the farmer, the tractor, has also evolved with the changes in modern agriculture to meet the requirements of these newer tasks. Larger, more capable vehicles have been introduced to help farmers efficiently meet these demands. At the same time, the current generation of tractor diesel engine lubricants has facilitated high levels of performance in the agricultural equipment market for many years. This is a testament to the role modern lubricants play in productivity in such a critical industry. With a growing global population to feed, and government regulations requiring reduced emissions for off-highway (OH) equipment, it is important to become more efficient in the ability to grow sufficient crops. One area worth investigating is the impact of engine lubricants on fuel efficiency. To quantify the improvement in fuel efficiency, full-scale farm tractor tests were conducted at the Nebraska Tractor Test Laboratory (NTTL). The scope of the experiment was to evaluate observable vehicle fuel economy improvements provided by various fresh engine oils. Testing showed improvements in specific fuel consumption (SFC) of nearly 2% when comparing an American Petroleum Institute (API) FA-4 oil to an API CJ-4 baseline. Furthermore, a strong relationship between high-temperature high-shear viscosity (HTHS) and SFC was observed.