In this study, engine performance, exhaust emissions and combustion behaviors of a single-cylinder, four-stroke, direct-injection diesel engine running on biodiesel/diesel/1-butanol and biodiesel/diesel/n-pentanol fuel blends were investigated and compared with diesel fuel under different engine speeds and full load operating conditions. Test fuels were prepared with 5 and 10 vol% 1-butanol and n-pentanol. Engine test results indicated that brake powers and torques decreased as the amount of alcohol increased, white BSFC increased between 0.77% and 8.07%. Alcohol blended fuels acquired lower EGT and CO2, while observing higher O-2 emission due to high oxygen content of alcohol compared to diesel fuel. Alcohol treated blends also diminished NOX by 0.56-2.65%, CO by 6.90-32.40%, and smoke by 10.47 -44.43%. Moreover, n-pentanol blended fuels showed better performance and emission results than 1-butanol blends. Maximum in-cylinder pressure of higher alcohol blended fuels found between 94.55 and 95.82 bar at 371-372 degrees CA for 1400 rpm, and between 78.19 and 82.19 bar at 375-376 degrees CA for 2600 rpm. Alcohol addition into the blends increased maximum in-cylinder pressure up to 1.38% at low speed, whereas it decreased up to 3.75% at high speed. Furthermore, higher HRR values up to 8.5% were observed with the alcohol mixed fuels. Consequently, higher alcohols (n-pentanol and 1-butanol) can be utilized as alternative additives in biodiesel/diesel blends for diesel engines to improve emissions, although they adversely influence engine performance. (C) 2018 Elsevier Ltd. All rights reserved.