Vehicle fuel filling may not occur the fastest way, mainly due to the filler neck geometry and low fuel flow from the pump. When the fuel tank in empty, the previous interferences are increased, once the inner pressure increases, complicating even more the fuel filling activity. Another problem that occurs due to poor filler neck design is fuel pump nozzle shut off, once the fuel flow can’t overcome the tank inner pressure causing fuel to return, turning off the pump or even leakage.The recent advances in CFD Codes and computational power allowed multiphase simulations to be performed in production level by the industries worldwide. This paper takes advantage of these advances and proposes a methodology for fuel filling simulation using multiphase CFD simulation in order to evaluate a filler neck design, by measuring the total filling time. The second part proposes a parametric analysis of the tank pressure, considering 2 fixed values and one fuel tank pressure curve measured from a physical test, in order to evaluate drop pressure and filling time.The methodology proposed is able to reproduce the fuel filling action into the virtual world, making possible to evaluate filler neck designs before any physical prototype is available.