Section § 80.41(i) of the federal regulation requires that during each calendar year 1995 through 1997 any refinery or importer shall be subject to the simple model standards or the Phase I complex model standards, at the option of the refinery or importer.

However, no refinery or importer may be subject to a combination of the simple and complex model standards during the same calendar year. Any refiner or importer that elects to achieve compliance with the anti-dumping requirements can use either the simple or complex model but must meet the requirements of Subpart D of these regulations for the specified model.

If the refiner or importer elects to use the complex model during a period prior to January 1, 1998, then the refiner or importer is subject to the Phase I complex model standards. Therefore, if a refiner or importer elects to use the simple model beginning on January 1, 1996, the regulations prohibit switching to the complex model on March 1, 1996 or at any other time during the same calendar year.(7/1/94)

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)