<p>The conventional methods to increase heat dissipation rates have their limitations due to poor heat transfer properties of base fluids and clogging of flow passages in case of micro fluids. Hence, research has been focused on use of nano-materials as heat dissipating medium, termed as “Nanofluid”. The performance of nano-fluid largely depends upon its stability. However, challenges in use of nano materials as dispersions is their long-term stability. In the present study, the experimental investigation carried out by preparing graphene nanofluid using two different sonication methods i.e. indirect sonication by bath type sonicator and direct sonication by probe type sonicator. The stability analysis carried out by sedimentation photograph method, Dynamic Light Scattering, Zeta potential technique, FESEM analysis and pH measurement. It was observed that by addition of Sodium Dodecyl Sulphate Surfactant, the stability of nanofluid improved and remained stable for more than 30 days. The quantitative values of stability in terms of absolute average zeta potential achieved more than 45mV and Polydispersibility index was less than 0.3, which indicates good stability of nanofluid. From the analysis, it is concluded that the stability of nanofluid prepared from hydrophobic nanoparticles depend on sonication methods, use of surfactant and pH value. The purpose to analyze the stability of graphene nanofluid is for its application as heat exchange medium. The long-term stability of nanofluid ensures longer shelf life of nanofluid, which further conserves its thermophysical properties.</p>