www.ext.vt.edu Produced by Communications and Marketing, College of Agriculture and Life Sciences, Virginia Polytechnic Institute and State University, 2014 Virginia Cooperative Extension programs and employment are open to all, regardless of age, color, disability, gender, gender identity, gender expression, national origin, political affiliation, race, religion, sexual orientation, genetic information, veteran status, or any other basis protected by law. An equal opportunity/affirmative action employer. Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; Jewel E. Hairston, Administrator, 1890 Extension Program, Virginia State, Petersburg. VT/1014/BSE-175P Publication 442-073 Introduction Ability to predict tractor fuel consumption is very use- ful for budgeting and management. The objective of this factsheet is to develop relationships using ield measurements and Nebraska Tractor Test Laboratory results to estimate tractor fuel consumption. Using these equations, farmers can estimate and compare the fuel consumption for different operating and loading conditions. Depending on the type of fuel and the amount of time a tractor or machine is used, fuel and lubricant costs will usually represent at least 16 percent to over 45 percent of the total machine costs. Thus, fuel consumption plays a signiicant role in the selection and management of tractors and equipment used in agriculture. Currently, most budget models use a simpliied methods for esti- mating fuel consumption. Better estimates representing actual ield operations are needed to compare machin- ery management strategies. The worth of a tractor is assessed based on work output and the cost associated with completing the task. Draw- bar power is deined by pull (or draft) and travel speed. An ideal tractor would convert all fuel energy into use- ful work at the drawbar. However, due to power losses, not all fuel energy is converted into useful work. Eficient operation of farm tractors may depend on: (1) maximizing the fuel eficiency of the engine and the mechanical eficiency of the drivetrain, (2) maximiz- ing tractive eficiency of the traction devices, and (3) selecting an optimum travel speed for a given tractor- implement system. This factsheet focuses on methods to estimate and improve fuel eficiency of a diesel power unit. The Nebraska Tractor Test Laboratory (NTTL) has a long history of testing tractors and disseminating power and fuel consumption data. The NTTL is the oficial testing station for agricultural tractors in the United States. Tractors manufactured in the United States and other countries are tested, and NTTL publishes the test results. During standardized tests, the power is calculated and the corresponding fuel consumption is measured. The power at the power takeoff (PTO) is calculated from the torque and speed at the PTO. Draw- bar power is calculated from the drawbar pull and the forward speed of the tractor. For more details and for a sample test report, see Using Tractor Test Data for Selecting Farm Tractors, Virginia Cooperative Exten- sion publication 442-072. The Nebraska Tractor Test Laboratory (NTTL) has a long history of testing tractors and disseminating power and fuel consumption data. The NTTL is the oficial test- ing station for agricultural tractors in the United States. Tractors manufactured in the United States and other countries are tested, and NTTL publishes the test results. During standardized tests, the power is calculated and the corresponding fuel consumption is measured. The power at the power takeoff (PTO) is calculated from the torque and speed at the PTO. Drawbar power is calcu- lated from the drawbar pull and the forward speed of the tractor. Terminology Tractor manufacturers specify power output at sev- eral tractor locations, such as power takeoff, drawbar, hydraulic outlets, and electrical outlets. For each tractor model, the rated power output is measured at the rated engine speed. Typically, this power is measured at the PTO, and in this factsheet, it is referred to as “rated Predicting Tractor Diesel Fuel Consumption Robert “Bobby” Grisso, Extension Engineer, Biological Systems Engineering, Virginia Tech John V. Perumpral, Professor Emeritus, Biological Systems Engineering, Virginia Tech Gary T. Roberson, Associate Professor and Extension Specialist, North Carolina State University Robert Pitman, Superintendent, Eastern Virginia Agriculture Research and Extension Center, Virginia Tech