In commercial vehicles which generally have large capacity fuel tank, sloshing of fuel and its effect on the tank structure is very important aspect during fuel tank design. Dynamic pressures exerted by the fuel on baffles, end plates and tank shell during sloshing can lead to structural failures and fuel leakage problems. Fluid structure interaction simulation of automotive fuel tank sloshing and its correlation with physical test is demonstrated in this study.During physical sloshing test of 350 L fuel tank, cracks were observed on center baffle and spot weld failures developed on fuel tank shell. Same sloshing test was simulated for one sloshing cycle using fluid structure interaction approach in LS Dyna explicit FE solver. Water was used instead of fuel. Mesh free Smoothed Particle Hydrodynamics (SPH) method is used to represent water as it requires less computational time as compared to Eulerian or ALE method. Equation of State (EOS) was defined in LS Dyna using variable parameters of volumetric strain (EV1, EV2…etc) and constants (C1, C2…etc) in order to represent the nonlinear behavior of water accurately during sloshing event. High strain areas on baffle and end plates were studied. Locations of weld failures and cracks observed on the center baffle & shell during physical test correlated quite well with simulation results.Post correlation, fuel tank with modified baffle design was re-simulated and found to have improved performance in terms of reduced strain values. Same modified fuel tank design tested physically for target number of durability cycles in the lab and found to be meeting the requirements.This improved and proven CAE methodology thus became very important and reliable step in design and development of high capacity fuel tanks.