ethanol in and of itself has about half the BTU energy of real gas so if you run all alchohol you would have to burn twice as much. as you add ethanol to gas you have to increase the amount you burn at roughly the same rate. the stupidity is that our illustrious gov. wants everything to be more and more efficient all the while forcing us to us less and less efficient fuel.

So you are saying that with E15 we will burn about 7% more fuel, and or have to jet up about 7%

I personally dont know the % things change by, I am sure someone here does, but yes you would burn 7% or so more and the jetting would have to reflect that