Viscosity property of a fuel is a crucial point for internal combustion engine characteristics. Performance and emission parameters as well as injector's life of an engine is primarily effected by viscosity of the fuels. In present study, effect of high viscosity biodiesel fuels with hydrogen addition was investigated in a compression ignition engine. Biodiesels that are produced from Pongamia Pinnata and Tung oils were used as pure biodiesels as well as blended with low sulphur diesel fuel at the volume ratios of 50% and 75%. Furthermore, hydrogen gas was injected into intake manifold in order to evaluate its effect with the usage of high viscous liquid fuels. The results revealed that brake specific fuel consumption was increased with biodiesel fuels, whereas hydrogen addition into intake manifold improved the consumption. Total vibration acceleration of the engine reduced with biodiesel and hydrogen additions. Frequency spectrum indicated that this decrement was primarily lowered due to less energy transmitted through engine pistons that converted from chemical energy of fuels. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.