The Finnish pulp and paper company, UPM, will start a biorefinery in Finland in 2014 to produce advanced renewable diesel in commercial scale. The fuel production is based on using crude tall oil (CTO), a wood-based residue of pulping process, as a raw material. The end product, CTO based renewable diesel called UPM BioVerno, is a novel high quality drop-in diesel fuel resembling fossil diesel. It reduces greenhouse gas emissions by up to 80 % when compared to fossil fuels.In this study, the CTO renewable diesel was studied as a blending component in regular mineral-oil based fossil diesel fuel in field testing. The functionality and performance of four (4) passenger cars was evaluated by comparing e.g. fuel consumption and exhaust emissions of CTO renewable diesel blend (R20UPM) with fossil reference fuel.The field test included 20.000 km on-road driving with each car by experienced drivers from VTT Technical Research Centre of Finland. The test included driving with variable trip lengths, traffic and climate conditions. Initial, mid-term and final in-laboratory tests were run for performance and emissions. Four other make/model cars were subjected to similar tests with R20UPM and reference diesel. Apart from regulated exhaust emissions, a list of non-regulated species was also measured. The main findings of these field and in-laboratory tests are discussed in this article.CTO renewable diesel proved to be a high quality blending component that did not change the functionality or the emission characteristics of the tested diesel passenger cars. There was no difference in fuel consumption or exhaust emissions compared to the reference diesel. Furthermore, use of test fuel R20UPM resulted in lower NOX emissions than if DFO fuel was used, on average. The test vehicle engines showed high performance in all conditions during the full length of the on-road test. The fleet test has therefore shown that CTO based renewable diesel works in passenger cars as well as regular diesel.