A model 6V92TA Detroit Diesel Corporation diesel engine (9.0 l) was fueled on blends of 10, 20, 30 and 40% soydiesel/diesel fuel. The engine was tested using the Environmental Protection Agency (EPA) heavy-duty engine test cycle in an EPA certification test cell. A 56.6 m(3)/min (2000 cfm) PDP-CVS dilution tunnel, gaseous bench and particulate bench provided full gaseous and particulate emissions data. Fueling with biodiesel/diesel fuel blends reduced particulate matter (PM), total hydrocarbons (THC) and carbon monoxide (CO), while increasing oxides of nitrogen (NOx). The optimum blend of biodiesel and diesel fuel was a 20/80 biodiesel/diesel fuel blend. Retarded fuel injection timing reduced NOx emissions, while CO, THC and PM remained essentially constant with a 20/80 biodiesel/diesel fuel blend. Copyright (C) 1996 Elsevier Science Ltd.