E85 is an abbreviation typically referring to an ethanol fuel blend of 85% ethanol fuel and 15% gasoline or other hydrocarbon by volume. In the United States, the exact ratio of fuel ethanol to hydrocarbon may vary according to ASTM 5798 that specifies the allowable ethanol content in E85 as ranging from 51% to 83%. This is due to the lower heating value of neat ethanol making it difficult to crank engines in relatively cold climates without pre-heating air intake, faster cranking, or mixing varying fractions of gasoline according to climate. Cold cranking in cold climates is the primary reason ethanol fuel is blended with any gasoline fraction.