http://www.epa.gov/otaq/regs/fuels/rfg/420f06020.htm

The U.S. Environmental Protection Agency (EPA) is amending the reformulated gasoline (RFG) regulations to remove the oxygen content requirement and associated compliance requirements. Because the 2005 Energy Policy Act provided for different compliance dates for the removal of the RFG oxygen requirement in California and the rest of the country, EPA is implementing the removal of the oxygen requirement in two separate rules. One direct final rule removes the RFG oxygen requirement and related compliance requirements for California gasoline. The effective date for this rule is 60 days from the date of publication of the rule. The other direct final rule removes the oxygen requirement for RFG nationwide. The effective date for this rule is May 5, 2006, (270 days from enactment of the Energy Act), or 60 days from publication of the rule in the Federal Register, whichever is later.
These direct final rules also revise the current prohibition against combining volatile organic compound (VOC)-controlled RFG blended with ethanol with VOC-controlled RFG blended with other oxygenates. The revision also prohibits combining VOC-controlled RFG blended with ethanol with non-oxygenated VOC-controlled RFG, except in limited circumstances authorized by the Energy Policy Act of 2005.