Section 80.78(a)(7) provides that "no person may combine any reformulated gasoline blendstock for oxygenate blending with any other gasoline, blendstock, or oxygenate...," and § 80.78(a)(7)(ii), states that an RBOB may be combined with "other RBOB for which the same oxygenate type and amount (or range of amounts) was specified by the refiner or importer." In addition, guidance was provided in the April 18, 1995 Question and Answer document that parties may consider the oxygenate amount specified for RBOB to be a minimum specification, and oxygenate may be added in excess of that minimum up to the applicable oxygen maximum or substantially similar maximum.
As a result, a party could combine RBOB's that have different requirements for oxygenate amount (but not different oxygenate types), provided that the mixture is designated for oxygen blending with the largest oxygen amount specified for any of the RBOBs in the mixture. For example, a party could combine any-oxygenate RBOB with RBOB designated for blending with 10 vol% denatured ethanol, as described in the question, provided that the mixture is designated for blending with 10 vol% ethanol. (8/29/95)
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)