A number of studies have demonstrated that biodiesel is a more environmentally sustainable fuel than petroleum-derived fuels since it is a renewable source of energy and it allows to reduce undesired exhaust emissions (e.g. unburned HC, CO and particulate matter). However, specialized literature highlights there is still the need to further investigate performance, emissions and NVH characteristics of engines equipped with up-to-date technologies fueled with biodiesel blend. The aim of the present paper is to investigate the vibro-acoustic behavior of a small displacement engine, mainly employed in micro-cars, fueled with blends of distilled biodiesel (obtained from used cooking oil) and ultra low sulfur diesel fuel up to 40% by volume. Demands for reducing chemical and noise pollutions, traffic congestion and parking difficulties in urban areas make the micro-cars one of the possible solutions for the future urban environment, especially if the engine is fueled with biodiesel blends for their potential of reducing the pollutant emissions. An original methodology developed by the authors for in-cylinder pressure characterization via non intrusive measurements is here applied to evaluate the impact of biodiesel content on the combustion process and therefore on engine vibration and noise emissions. The data processing in frequency domain allowed to extract the components mainly related to the combustion events. Concerning vibration signals: for all blends,the vibration amplitudes increases with the increase of engine speed values; B40 is characterized by highest values of RMS of accelerometer signal almost in the complete engine operative field. RMS values obtained for B10 are the lowest ones in most of the investigated engine operative conditions. Concerning noise radiation: the Noise Index was used to evaluate the components of the emission where the combustion energy demonstrated to be concentrated. The results show an increase of Noise Index for all blends with the increase of engine speed. B10 is characterized by the highest values in most of the testes conditions. B40 values demonstrated the opposite behavior. (C) 2016 Elsevier Ltd. All rights reserved.