the smart part of their process is when they talk about making hydro carbon chains of more similar and consistent size. The black smoke, smell, and bad fuel milage comes from improper or incomplete combustion.
If for example, you had a range of hydrocarbon chain from 6-12 links long, the 6,7,8,9 link long hydrocarbons would burn completely, and the 10,11,12 wouldn't have time to burn completely. This is why when diesel vehicles switch to propane (a much shorter hydrocarbon chain) then you have fewer emissions. BUT, by having too few hydro-carbons, then you begin to have much less energy going in to the combustion chamber therefore require more overall fuel.
Gdiesel takes a smart approach by basically increasing the surface area of the hydrocarbon chains while still keeping a long carbon hydro-carbon chain, so the energy stays.
How this produces IN SOME CASES 50% BETTER FUEL MILEAGE?
This is of course a marketing piece. Take it for what it is.
Maybe if you use Gdiesel with magnets and a tornado intake you car will not use any fuel what so ever.