The scope of this work is to examine the use of hydroprossed used cooking oils as substitute for automotive diesel fuel. Hydroprocessing is an alternative method for the transformation of vegetable oils into high quality transport fuels, even if the quality of the oils is low, such as used cooking oils. In the present work, the utilization of hydroprocessed used cooking oil (HUCO) as neat fuel was proved to be very difficult, due to its very poor cold flow properties; therefore, mixtures of the HUCO with low quality middle distillates (a low cetane number gasoil and a light cycle oil) were prepared and evaluated. Throughout the process the formed blends were evaluated according to the european standard EN 590. The following points were mainly recorded: The lower density of HUCO was beneficial, permitting the use of poor quality distillates, in specific concentrations, and the high cetane number of HUCO was appreciable, improving the worse behavior of the other components. On the other hand, some downsides of HUCO have been enhanced by blending, with the low quality middle distillates. The cold flow properties of HUCO were inferior for direct use in diesel engines even in temperate climates. The blends with low cetane number gasoil (LCN) and light cycle oil (LCO) allowed the addition of HUCO in a specific content, leading to a “summer grade” fuel, appropriate for utilization in Greece and the warm Mediterranean region. The conformance with EN 590 requirements is easier for the low cetane number gasoil, compared to the very high density LCO. Therefore, the utilization of HUCO as a biocomponent should further be investigated, since it may be valuable as blending component for the upgrade of low quality middle distillates.