I took for granted he meant the E-85.
The 30% reduction in the energy of the molecule translates to a 30% reduction in mileage.
I am convinced, as well. that a 90/10 blend reduces mileage in my Silverado by at least 10%.
And I track my mileage nearly every fillup.
We've experience her in Denver with the 10% blends and I despise them for the reduced mileage.
In an internal combustion engine, the lower heat content of alcohol can be offset by certain advantages in its combustion properties. Alcohol is less volatile than gasoline, so the timing can be advanced and the stroke can be lengthened. Its lower volatility gives it a much higher octane rating (denatured alcohol has an octane rating of 113, as I recall), which means that it can power a much higher compression engine. Its latent temperature of evaporation makes it ideal as a fuel in a supercharged engine.
The current problem with alcohol as a fuel is that engines which are tuned for gasoline will run on alcohol, just with a loss of economy. Low octane gasoline won't run worth a hoot in an engine tuned for alcohol.