In the development of the Complex Model, EPA investigated the possibility that two complying batches, when mixed, may not comply with the RFG standards. This "fungibility" issue arises out of the model's nonlinear character. Based on a Monte Carlo simulation, EPA concluded that fungibility problems would not occur. The downstream standards adopted by EPA apply to each gallon of gasoline, including fungibly mixed gasoline.(11/10/97)

This question and answer was posted at Consolidated List of Reformulated Gasoline and Anti-Dumping Questions and Answers: July 1, 1994 through November 10, 1997 (PDF)(333 pp, 18.17 MB, EPA420-R-03-009, July 2003, About PDF)