The boron occupies an important place on contributions and its usage is getting widespread. Although the use of boron-added mineral oils serves to reduce friction, environmental risks can not be totally removed. It is necessary to improve the properties of biological oils used for additives so that they can compete with mineral oils technically. In the study, the use of liquid boron as an additive for engine lubrication oil together with vegetable oil was investigated experimentally in two diesel engines. Experiments were first carried out using mineral lubrication oil in the engine, and then the experiments were repeated using mineral base oil with additives in the second engine with the same technical characteristics as the first engine. Basically, the study was performed in the fields of engine performance (torque, power, consumption per hour, specific fuel consumption) and exhaust emissions (CO, CO2, HC, O2, SO2, NOx). As a result, it was concluded that the engine, in which boron and mineral oil with wild mustard oil were used, provided more significant fuel saving than in the engine with additive-free mineral oil, and no significant change was seen in the engine performance, also they showed similarities in terms of exhaust emissions.