In the current environmental and socio-economical scenario, the urgent need for reducing pollutants and greenhouse gas emissions from road transport has brought the development of innovative technologies as well as the finest optimization of the yet-established ones. Alongside with the continuous improvement of engine efficiency and the definitive abatement of engine air-pollutant emissions, the technical research on the last-generation Compression Ignition (CI) Engine is pursuing the goal of reaching minimum CO2 emissions. In this scope, Dual Fuel (DF) Hydrogen-Diesel Internal Combustion Engines (ICE) come into play, maximizing the Hydrogen Fuel Substitution rate, and exploiting Diesel Fuel as an ignition source to compensate for the high self-ignition Temperature of the H2 fuel.