In this study, bioethanol produced from waste bread by fermentation was evaluated as engine fuel comparing with sugar beet bioethanol purchased. Comparison criteria are parameters of combustion analyses, engine performance and exhaust emissions. Therefore, the experiments were carried out in a single cylinder, four stroke, air cooled SI engine fueled with both bioethanol blended with gasoline in different proportions for different test conditions created with different engine load and a constant engine speed. Whether formed with sugar beet or waste bread bioethanol, fuel blends with similar volumetric contents have similar trends in every sense and their position they take relative to pure gasoline is similar. But when the ones with similar content are compared with each other, the differences emerge. These can be summarized as follows: It has been determined that combustion occurs in a shorter time with lower maximum cylinder pressures and maximum heat release rate if the engine runs with fuels containing waste bread bioethanol. In the case of adding waste bread bioethanol, there was a gradual increase in brake specific fuel consumption and a gradual decrease in thermal efficiency compared to sugar beet added fuels. The use of waste bread bioethanol blended with gasoline has seriously positive results in many emissions aspects such that it has less CO up to 70.9%, less HC up to 34.9% and less NOx up to 5.1%, except for the fact that it has more CO2 up to 3.5%.