The objectives of this study are to investigate the effect of a diesel fuel blend with n-butanol on the individual hydrocarbons and particulate matter (PM) of a turbocharged common rail direct injection diesel engine and to compare the results with the neat diesel fuel operation case. The emission characteristics were estimated by using 5%, 10%, and 20% (by volume) of n-butanol blended with conventional diesel fuel. The measured emissions were the regulated emissions of total hydrocarbons (HC) or individual HC, CO, NOx, PM and the non-regulated emission of formaldehyde, which were measured under three different engine loads (25.4, 52.9 and 78.4 N m) and three different engine speeds (1500, 2000 and 2500 rpm). It was found that more ethylene and benzene are emitted under low load condition, and that their amounts increase with increasing n-butanol blend ratio. The fuels blended with over 10% butanol produced higher non-regulated formaldehyde (HCHO) emission than the neat diesel fuel under lower engine load conditions. The particle numbers for particles smaller than 50 nm were higher for the fuel blended with 20% butanol in diesel fuel compared to the neat diesel fuel. From the TEM images, it was found that a larger number of individual particles with a size of 10-30 nm were stacked on top of each other in a circular pattern. (C) 2015 Elsevier Ltd. All rights reserved.