Ethanol for use in automotive fuels can be made from renewable feedstocks, which contributes to its increased use in recent years. There are many differences in physical and chemical properties between ethanol and petrochemicals refined from fossil oil. One of the differences is its energy content. The energy content, or heating value, is an important property of motor fuel, since it directly affects vehicle fuel economy. While the energy content can be measured by combustion of the fuel in a bomb, the test is time-consuming and expensive. It is generally satisfactory and more convenient to estimate that property from other commonly-measured fuel properties. Several standardized empirical methods have been developed in the past for estimating the energy content of hydrocarbon fuels such as gasoline, diesel fuel, and jet fuel. However, the addition of ethanol to gasoline has become very common in some countries, and most of the estimation methods developed for hydrocarbon fuels are not satisfactory for use with gasoline-ethanol blends, especially blends containing more than about 10 volume-percent ethanol. This paper summarizes heating value test results from recently collected retail samples of gasoline-ethanol blends in the U.S. for E10 and E85 blends and in Brazil for E20 and E100 blends, as well as laboratory blends of different levels of fuel ethanol. The heating values obtained by different standardized test methods are compared and discussed. New empirical equations are proposed for gasoline fuel blends containing ethanol.
