An experimental study is carried out to examine and analyze the influence of Di-Tertiary Butyl Peroxide in bioethanol diesel blends on the performance, combustion and emission characteristics in a single cylinder, 4-stroke, naturally aspirated, automotive diesel engine for variable speed at full load conditions. Esterified cotton seed oil of 5% by volume is emulsified with 95% pure diesel to get the base fuel (BEO) for the experiments. Bioethanol diesel blends are produced from base fuel by adding 5% and 10% pure ethanol on a volumetric basis to obtain BE5 and BE10 respectively. The bioethanol fuels are low in Cetane number and hence Di-Tertiary Butyl Peroxide a Cetane enhancer is added by 0.4% by volume to produce BE5CN0.4% and BE10CN0.4% emulsions respectively. It is found from the experiments carried out, that an inverse trend exists between brake thermal efficiency and percentage of ethanol in base fuel. This is due to the lower calorific value of ethanol and an improvement in brake thermal efficiency is observed with ignition improver added blends. The presence of Cetane improver significantly reduced oxides of nitrogen and unburned hydro carbon emissions for overall engine speed and carbon monoxide emissions for low to medium speed range. (C) 2016 Elsevier Ltd. All rights reserved.