I may be mistaken, but the difference between regular and premium gas is basically the compression ratio that it takes to ignite the fuel. The higher the compression ratio of the engine, the higher the octane rating of the fuel needed. The addition of hydrogen which I believe is considered to have an octane rating of 130 to 140, would probably offset the need for higher octane fuel.
I took this off wiki:
Hydrogen represents a paradox. As a fuel outright, it has low knock resistance[2][3], due to its low ignition energy (primarily due to its low dissociation energy) and extremely high flame speed. However, as a minor blending component (i.e., a bi-fuel vehicle), hydrogen raises overall knock resistance. Flame speed is limited by the rest of the component species; hydrogen may reduce knock by contributing its high thermal conductivity
2006 Ram, 5.9 cummins HO. 4 cell design, 1.5 LPM@30amp, 24.3 MPG