To "expunge" means to erase or wipe out. "Exsponge" is both more apt and true development of language.

I still maintain that B7 diesel is, by my calculations above, 8.33% less efficient than "normal" diesel. So for the same amount of work, one is burning an extra 0.74% of fossil fuel (and an extra 0.058% of your environmentally conscious biofuel). By these calculations, B7 fuel is an extra three quarters of one percent worse than things were before. To save on fossil fuel usage, at least 9% of diesel fuel must be biofuel, and there is no guarantee that this would make diesel engines even less efficient.

And, by the way, my B7 chords all sound as if they were penned by Enio Morricone (either bad or ugly).