This study is focused on investigating the regulated and unregulated emissions of a 4-cyclinder natural-aspirated direct-injection diesel engine fueled with neat diesel fuel, B10 (diesel containing 10 vol.% of biodiesel), B20, B30 and neat biodiesel (B100). Experiments were conducted on the Japanese 13-mode test cycle for the diesel engine so that the influence of engine load and engine speed on the regulated and unregulated emissions can be identified. The 13-mode weighted results show that with an increase of biodiesel in the blended fuel, there are reductions of HC, CO and particulate mass concentrations but an increase in NOx. For the unregulated emissions, formaldehyde and acetaldehyde emissions increase with increasing biodiesel content. The same trend can be observed for 1,3-butadiene, propene and ethene. For the aromatics emissions, biodiesel addition leads to an increase in benzene emission but reductions in toluene and xylene emissions. The results also show that all the emissions are affected by the engine operating modes, especially the engine load. (C) 2016 Elsevier Ltd. All rights reserved.