The Fuel Freedom Foundation decided to find a definitive answer this question for both ethanol and methanol. In the introduction to their white paper entitled, Is the Gasoline Gallon Equivalent an Accurate Measure of Mileage for Ethanol and Methanol Fuel Blends?, Eyal Aronoff and Nathan Taft wrote:
A presentation composed by Henry Joseph Jr. — the Product Technology Emissions Laboratory & Engine Test manager of Volkswagen Brazil — for the Brazilian Vehicles Manufacturers Association claims that ethanol performance in Brazilian vehicles is nine percent higher than predicted by energy content. Meanwhile, a study conducted by the University of Riverside claims despite a lower energy content, higher efficiency is obtained from ethanol in optimized engines.
Alcohol gets better mileage than we have been led to believe. This is an important point for many reasons. On the other hand, it may be less important for individual drivers because proponents of fuel competition are not suggesting we do away with gasoline. Once the U.S. has achieved fuel competition, whenever a driver wants to buy a fuel with greater energy density (for a longer trip or fewer refuelings, or for whatever reason), the driver will be able to put gasoline in the car (or butanol, when that becomes available).
This is one of the biggest advantages of cars that allow true fuel competition: They allow the driver to choose. If you would like to see fuel choice and competition in America, there are many things you can do to help. Here are some ideas.
Read more: Gasoline's Greater Range.