Internal combustion engines will play a major role in road transportation during the next decades. However, based on the legislative actions, the abatement of GHG emission is an important task in the production of future fuels. Waste and renewable based fuels can play an important role in the future. Though, there are many open questions in these fields. The main target in future is to develop new and economical technologies providing excellent quality advanced fuels, having low heteroatom, aromatic and olefin content. Nowadays, biodiesel is the most commonly used bio-component in diesel fuels. Bio gas oil is an alternative bio-fuel which can be produced from triglycerides/fatty acids by catalytic oxygen removal reactions. Diesel fuel blending components with bio-component can be obtained from the co-processing of fatty acids and different crude oil-based gas oil fractions. The aim of our experimental work was to monitor the long-term stability and performance of a commercial, sulphided NiMo/Al2O3P hydrotreating catalyst. We studied the catalytic hydrogenation of fatty acid mixture (5 %) and gas oil with high aromatic and sulphur content producing valuable diesel blending components. The effect of temperature, pressure and space velocity on the quality and quantity of the gas oil products were investigated in the long term tests. Based on the experimental results diesel fuel blending components with high hydrogen content can be economically produced in the studied catalytic system with minimal or negligible change in the activity of the catalyst after 472 h. The most favourable process parameters were the followings: P = 70 bar, T = 350 – 360 °C, LHSV = 1.2 – 1.5 h-1, at hydrogen/feedstock ratio = 400 Nm3/m3.