The use of different rates of biodiesel fuel in diesel engines is a very effective method for reducing exhaust emissions without causing excessive performance losses under certain engine operating conditions. In many countries, 5% biodiesel fuel contribution has become mandatory, and this ratio is much higher in some countries. In this study, addition of 5%, 10% and 15% ethanol and methanol to diesel fuel on engine performance and emission behaviour in a four-cylinder diesel engine were investigated using AVL Boost v2018.1 software. When 5%, 10% and 15% of ethanol is added to diesel fuel, the power is dropped 5 %, 4 % and 5 % compare to pure diesel usage, respectively. In the addition of methanol, these percentages were become 5 %, 5 %, and 8 %. With the addition of ethanol, the NOx reduction rates are 25%, 27%, and 28%, respectively. In the usage of methanol, these emissions were reduced 27%, 28%, and 30%, respectively. In the formation of soot, both ethanol and methanol use has been found to vary depending on the engine speed.