Scania provides sustainable transport systems powered by bioethanol, biogas, biodiesel along with hybrid and conventional solutions. Today Scania offers the largest variety of engines operating on alternative fuels in the market. The number of the alternative fuel operated vehicles sold in 2016 increased by 40 % [1]. Nevertheless, one of the alternative fuels – biodiesel - is a source of inorganic contaminants. These impurities can detrimentally affect the diesel truck after-treatment system that is responsible for harmful emission abatement. As a consequence, better understanding of the alternative fuel impact on the after-treatment system is necessary for further development of a sustainable transportation system. This thesis is focused on the diesel oxidation catalyst (DOC) that is one of the major components in the diesel truck after-treatment system. Catalyst performance due to chemical deactivation of biodiesel derived inorganic contaminants (P, Na and Ca) is determined and analysed. The study covers PtPd/Al 2O3 DOC preparation and poisoning by the incipient wetness impregnation method, monolith dip-coating, fresh and poisoned catalyst characterization (BET, CO chemisorption, TPR, ICP-OES, TEM-EDS, SEM-EDS, XRD). Catalyst activity tests in a laboratory scale activity testing rig are performed to study carbon monoxide, nitric oxide and propylene oxidation reactions before and after the poisoning. Sulphur effect on the catalyst activity is determined after the gas-phase poisoning with SO2.