The transition to low-carbon mobility could lead to drastic increases in critical mineral requirements risking adverse ecological and societal impacts. Assessments of climate change mitigation potential of new technologies often pay less attention to the criticality of the enabling minerals. We assessed the effects of adopting 4 hybrid architectures on the life-cycle GHG emissions of an emerging fuel and powertrain solution: the use of a novel high-reactivity fuel in an advanced compression-ignition engine (GCI). The 4 hybrids were contrasted against conventional fuels/engines, and a comparable battery electric vehicle using regionally-explicit power mixes in the 3 biggest automotive markets worldwide (China, USA and Europe). The use of larger batteries enabled higher degrees of electrification and it could lead to lower overall emissions. However, there is diminishing returns for every kWh of increasing battery size: a mild hybrid resulted in more than 50% GHG reduction per kWh of battery, whereas an electric vehicle only reduced emission by 4% per kWh given its much larger battery requirement. Given the sustainability constraints of critical raw minerals supply, and the heterogeneity of regional power grids, advanced GCI hybrid architectures, with varying degrees of electrification, can bridge the gap in the interim.