No, ethanol has a lower energy density, but not that much lower as to make a huge difference.
Wikipedia has a handy table with the energy density of various fuels used in tranportation [1]. The net energy density per liter of regular gasoline is 32.2 MJ (megajoules). For gasoline with alcohol (which they call gasohol) it is 31.3 MJ. So gasohol has an energy density about 2.7% lower than regular gasoline, not 25% lower.
Wikipedia has a handy table with the energy density of various fuels used in tranportation [1]. The net energy density per liter of regular gasoline is 32.2 MJ (megajoules). For gasoline with alcohol (which they call gasohol) it is 31.3 MJ. So gasohol has an energy density about 2.7% lower than regular gasoline, not 25% lower.
[1] https://en.wikipedia.org/wiki/Gasoline#Comparison_with_other...