[naturalextraction]

In the case of a diesel, the system that is in place, the electronic control systems implemented, flame front related to the dynamics of the diesel engine, etc, etc, flame front for diesel fuel is optimized in that environment. In and I.C.E. without the proper controls and trying to mix two very different hydrocarbon chains proposed for use in a particular environment to produce a particular out put, flame front is very important. So in now way am I saying flame front does not impact efficiency, I'm saying the systems created, related to an established Diesel or I.C.E., all ready has optimal efficiencies installed and designed accordingly. Its very rare that you would be able to make one single change to receive a larger gain.
Incorporating changes throughout the entire system follows along the lines of optimizing total system operational efficiencies.
Introducing a significantly faster burning fuel like hydrogen, of any significant amount that can produce work energy, would create pre-detonation of varying proportions. The key being "significant amounts to produce work energy". Supplementing a fuel with another has to be done in a way that they work together, and have enough compatibility chemically combined with the proper controls, to provide a desirable effect or have an advantage if there is one to be had.
In having different "blends" of racing fuel, induction and operating controls can change considerably.
The real point being, is that one would expend an enormous amount of energy (system related and cost) to create enough hydrogen (in relation to the necessary chemical energy) to achieve any short or long term benefits.
I'm very familiar with the studies related to hydrogen supplemented and hydrogen fuel cell hybrid design power plants. Again they use compressed hydrogen in cylinders, have lots of controls and the hydrogen is not produced via electrolysis on board the vehicle.