The analysis of the life cycle greenhouse gas emissions of various passenger vehicles and heavy-duty trucks indicated that hybrid electric vehicles powered by ethanol from sugar beet and hybrid electric trucks powered by synthetic diesel from wood had the lowest emissions. In addition, projections for future emissions indicated significant reductions, particularly for xEVs and vehicles powered by e-fuel. However, battery electric vehicles and trucks were found to have relatively higher emissions when powered by electricity from marginal sources. Therefore, it is desirable for powertrains powered by carbon-neutral fuels such as e-fuel, biofuels, and hydrogen to become the mainstream.