Biodiesel, the mono alkyl ester of long chain fatty acids derived from renewable lipid resources was evaluated for use as a blending agent with heavy alkylates and low sulfur petroleum diesel fuel. The engine selected for testing was a 1992 L10E Cummins diesel engine. The regulated EPA exhaust emissions of the engine were evaluated before and after retarding the injection timing of the engine by 3°. EPA exhaust emissions were also evaluated after increasing the concentration of biodiesel and heavy alkylate while reducing the low sulfur diesel fuel used when fueling the engine. In general, the engine performed well and power changed very little during the testing. All EPA regulated exhaust emissions were reduced below that observed when fueling with baseline low sulfur diesel fuel as a result of timing changes and/or fueling with heavy alkylate blends.