Reducing the greenhouse gas emissions is one of the most important targets in the automotive industry and to do so, a shift to carbon-neutral fuels is one of the most promising alternatives. Due to their composition, hydrotreated vegetable oils (HVOs) are very high quality bio-based diesel fuels, with no negative effects on engines or exhaust after treatment system. In partnership with ENI, a research activity at the Energy Department in Politecnico di Torino has been started to investigate the effects of using HVO instead of a conventional diesel fuel. The first step has been the development of a CFD model of a light-duty commercial vehicle equipped with a compression-ignition engine powered with conventional diesel fuel.