This paper focuses on the hydraulic losses of the low-pressure diesel fuel path and the impact of these losses on the fuel consumption and therefore CO2 emissions of internal combustion engines. In this context, a 1D (one-dimensional) simulation model with implemented fluid flow physics was developed. A 3D CFD model for considering complex geometries of several fuel path components further enhances the 1D approach. Experimental data from a test bench, carrying the complete fuel pressure system, were used for validations and continuous developments of the simulation models. The results show a substantial potential of the low-pressure system regarding a reduction of CO2 emissions, depending on the control strategy of the electric fuel pump and the geometrical properties of the fuel pipes and couplings. Within the New European Driving Cycle, a potential of up to 1.1 g CO2/km was observed.