In this article the effect of waste heat recovery (WHR) system by means of Organic Rankine cycle (ORC) on passenger car engine fuel consumption was studied. A vehicle driving model was developed in order to determine the engine operating points in New European Driving Cycle (NEDC). In order to evaluate exhaust gases enthalpy and fuel consumption at engine operating points corresponding to the driving cycle the engine was experimentally tested in steady mode. The exhaust gases temperature was measured at a location situated 1.5 m downstream the exhaust valves considering that place as the inlet of ORC heat exchanger. A simulation model of ORC was developed using R245fa as a working fluid. Numerical results revealed that maximum recovered power was 1.69 kW. The contribution of the WHR system on the vehicle fuel consumption was assessed by reduction in cumulated fuel consumption for a NEDC. Applying an ORC to engine exhaust gases reduces cumulated fuel in a NEDC test from 0.441 to 0.414 kg. In relative values this reduction accounts to 5.9 %.