The aim of the present study was to evaluate the effect of using n-butanol in vegetable oil-diesel fuel blends on engine performance and exhaust emissions of a direct injection diesel engine operating at full load (100% throttle conditions) with different engine speeds without any engine modification. Neat canola-hazelnut-cottonseed oil (CHC) and neat sunflower-corn-soybean oil (SCS) blends were prepared as equal vol.% by splash blending method. Diesel fuel (70 vol.%) and n-butanol (10 vol.%) are added into CHC and SCS blends (denoted as DCHCnB and DSCSnB, respectively), simultaneously. Basic fuel properties of DCHCnB and DSCSnB are similar to those of diesel fuel. According to engine performance and exhaust emission test results of DCHCnB and DSCSnB, average values of brake torque (-6.08% and -6.67%), brake power (-4.12% and -4.59%), brake thermal efficiency (BTE) (-10.80% and -11.66%), exhaust gas temperature (-15.11% and -14.99%), carbon dioxide (CO2) (-1.12% and -2.30%) and hydrocarbon (HC) (-36.71% and -32.28%) are lower, while brake specific fuel consumption (BSFC) (18.43% and 19.58%), oxides of nitrogen (NOx) (27.27% and 30.36%) and carbon monoxide (CO) (41.57% and 26.89%) are higher than those of diesel fuel. (C) 2014 Elsevier Ltd. All rights reserved.