In this work a new mercapto silane (3-Octanoylthio-1-propyltriethoxysilane) was successfully grafted onto styrene butadiene rubber using reactive mixing process. Silane grafted rubber / silica vulcanizates were prepared using an internal mixer and compression molding machine. Dispersion of silica in rubber matrix was studied by varying grafting weight percentage and the filler loading. Dispersion of silica in styrene butadiene rubber matrix was quantified by the dispersion degree parameter (Dispersion Index) using Scanning Electron Microscopy and Atomic Force Microscopy. The relationship between the Dispersion Index and physico-mechanical properties of the composites was established. Improvement of Dispersion Index with increasing grafting weight percentage was observed. Fourier Transform Infrared Spectroscopy showed rubber-silane and silane-silica interaction. A rubber-silane-silica network was also depicted in this work. The dispersion rate constant was calculated from the torque-time curve in Haake internal mixer. Improvement of dispersion rate constant with the grafting percentage indicated the improved rubber-filler interaction with grafting. Improved rubber-filler interaction for the grafted rubber/silica compound was shown by Bound rubber content, Filler Flocculation rate and Payne effect measurement. A relationship was formed between the low strain modulus of the composites and the grafting weight percentage of the base rubber. The rolling resistance of the composites improved with grafting percentage. Low strain mechanical properties of the composites were studied using nanoindentation testing. Physico-mechanical properties have shown constant improvement with grafting percentage and filler loading. From the improved mechanical and dynamic mechanical properties, it can be predicted that this method could be used in fuel-efficient tire applications.