The paper deals with hydrogen fuel as a cleaner alternative to other conventional fossil-based hydrocarbon fuels like RON 91 and CNG in SI engines. It is considered as the future fuel for power propulsion and mobility in various sectors and applications of the industry. H2 has various properties like no tailpipe emissions, other than steam including some amount of NOx (which could be reduced to a great extent using proper catalytic converters), other than these some good fuel like properties are high diffusivity, high calorific value, and low ignition energy, while some drawbacks are low volumetric energy density, backfire and knocking. A comparative study have been done using computerized 1-D simulation of a single cylinder, port-fuel injected, single spark ignition setup with all parameters of combustion and engine as same, running on RON 91, CNG and Hydrogen in equivalent values of lean, rich and stoichiometry equivalence ratios. Parameters like power, torque, BSFC, and NOx have been simulated and results have been analyzed for the three fuels. H2-CNG power and torque ranged from a loss of 11–22.5% and NOx has been lowered by 39% at lean equivalence ratios, while BSFC has been as low as 60% at lean equivalence ratios. With no un-burnt hydrocarbon emissions or other carbon-based emissions, proves that lean burn H2 can be a potent fuel for future mobility in case of CNG fuel replacement, while for RON 91 replacement modern technologies must be included to reduce the losses.