The article explores the impact of hydrogen on engine performance and emissions through various studies and experiments. Research on hydrogen enrichment effects on diesel engines operated with biodiesel blends is showing positive outcomes in terms of performance and emission characteristics. Additionally, studies on the use of ammonia/hydrogen mixtures in SI engines are indicating improvements in engine performance and the proposed fuel systems. Investigations into the usability of oxy-hydrogen gas are revealing its potential to enhance combustion, performance, and emission behaviors of CI engines. Moreover, experiments involving hydrogen addition to intake air in diesel engines and blending of ammonia and hydrogen in SI engines are leading to improved combustion stabilities and reduced emissions. Overall, the findings suggest that hydrogen, in its various forms, holds promise in contributing to more efficient and environmentally friendly engine operations.