Survey of Flex Fuel in 2014: CRC Project E-85-3

Teresa Alleman

Research output: NRELTechnical Report


ASTM D5798 sets the specifications for Ethanol Flex Fuel, which currently permits between 51 volume percent (vol%) and 83 vol% ethanol. The vapor pressure varies seasonally and geographically and is divided into four distinct classes to ensure year-round driveability. This project is the first survey of Ethanol Flex Fuel since these specification changes were made to Specification D5798. Ninety-one Ethanol Flex Fuel samples were collected in this project, across all four classes and throughout the United States. Four samples were collected in California, which has quality requirements different from the rest of the country. Samples from more than one class were collected from most stations visited. All samples were analyzed for vapor pressure, ethanol content, and water content. In this study, 60% of the samples met the relevant vapor pressure specifications, while 98% met the ethanol content specifications. Over 80% of the samples contained less water than the specification limit. Classes 2 and 3 had the most samples off specification for vapor pressure, with only 58% and 30% of the samples meeting the requirements, respectively. The Class 1 data contained several on-specification samples with high ethanol content and high vapor pressure, indicating they may be been blended with a higher vapor pressure blendstock relative to the other samples in the class. Compared to previous surveys, the water content in these samples was notably higher and more often exceeded the specification.
Original languageAmerican English
Number of pages25
StatePublished - 2015

NREL Publication Number

  • NREL/TP-5400-63503


  • D5798
  • E-85-3
  • ethanol flex fuel
  • quality survey


Dive into the research topics of 'Survey of Flex Fuel in 2014: CRC Project E-85-3'. Together they form a unique fingerprint.

Cite this