While this whole HHO, Brown's gas, water4gas, or whatever you want to call it is a scam and cant work, diesel engines run very lean most of the time, one of the many reasons they are more efficient. So, what is the problem with running lean for too long?

Unlike a spark ignition engine with a throttle, diesels always take in a full air charge with each intake stroke and vary the power output by regulating fuel flow. The latest direct injection gasoline engines, on some VW/Audi and Lexus, and was used on some large aircraft engines in the 1950's also allows for super lean mixtures. "Leaner is hotter" is a myth borne of 1960's attempts at crude emission controls with fixed jet carburators, going from way rich to slightly rich, which is hottest. Airlines and the military found that leaner is cooler, and cleaner, decades ago.

Jim