Future legislations claim further reduction of all restricted emissions as well as the limitation of soot emissions in diesel engines. Special alternative diesel fuels that do not contain aromatic compounds, therefore, promise great potential for further reduction of HC, CO and particulate emissions.During a research project carried out at the Institute for Powertrains and Automotive Technology at the Vienna University of Technology, the potential of alternative diesel fuels was investigated using a state-of-the-art diesel engine with common rail direct injection. The testing took part using an engine test rig as well as on the chassis dynamometer test bench to demonstrate the emission levels in real life conditions. As real biofuel, pure HVO (Hydrogenated Vegetable Oil) was investigated and additionally in different blends with fossil diesel fuel.The results on the engine test bench show that HVO can reduce the NOx-particulate trade-off up to 50% compared to conventional diesel, whereas this is not the case at all load points. Especially in low-load conditions, the high cetane number of the alternative fuel leads to a decreased ignition delay and thereby reduces the potential to lower particulate emissions.Besides the reduction of particulate emissions, the fact that HVO does not contain any aromatic compounds also helps to reduce unburned HC and CO emissions. For both, a reduction of up to 50% could be achieved compared to fossil diesel, whereas the magnitude of the decrease depends on the temperatures occurring during the combustion. Due to the fact that today's diesel engines often have low exhaust gas temperatures, the cold start phase is very important. During the time before the light off of the oxidation catalyst has taken place, low unburned raw emissions can mean a big advantage in real life conditions.Another important issue is the influence of different fuels on the oil dilution, especially during late injection events as necessary for the regeneration of particulate filters. In this case HVO leads to an increasing wall impact and thereby dilution of the lubricant oil.