[EN] As the world intensifies its efforts to reduce the adverse effects of global warming, the shift towards a fully developed hydrogen-based economy is emerging as a core strategy. This transition involves the strategic blending of hydrogen with conventional fossil fuels such as natural gas (HCNG), allowing for adaptation to hydrogen availability. Nevertheless, the environmental impact of HCNG vehicles in realistic scenarios with variable hydrogen content remains unexplored. This study focuses on evaluating the global warming impact of the transition of light-duty passenger cars from CNG to H2 vehicles using HCNG blends from 2020 to 2050 and different realistic scenarios. The results in the present study were obtained through a combination of an experimental testing campaign that allowed obtaining how the performance and emissions of HCNG vehicles change with the H2 content and a life cycle assessment methodology. Based on the findings, the scenario in which hydrogen was mostly produced from SMR-dominant, was found to have the potential to reach and outperform the zero-emission concept due to the utilization of biogas. From the results of this study, the recommended H2 content in HCNG blends that offers low environmental impact while avoiding the overdemand of hydrogen in the short term for the 2020-2030 decade is 25% H2 content, increasing to 50% by 2030, and to 75%-100% during the 2040-2050 decade, thus reaching the transition towards pure-H2 technology that minimizes environmental impact. This research has been partially funded by FEDER and the Spanish Government through project RTI2018-102025-B-I00 (CLEAN-FUEL) . M. Olcina-Girona is partly supported by the grant CIACIF/2021/437 of the "Subvenciones para la contratacion de personal investigador pre-doctoral (ACIF) "of the Conselleria d'Innovacio, Universitats, Ciencia i Societat Digital de la Generalitat Valenciana, Spain.