Yes. Oxygenate must be added to RBOB in the proper type and amount regardless of where it is sold. Specifically, section 80.77(a)(7) prohibits any person from combining RBOB with any other gasoline, blendstock, or oxygenate except oxygenate of the type and amount specified for the RBOB type or with other RBOB that has the same requirements related to oxygenate type and amount.
Furthermore, the RFG regulations contain other relevant and specific prohibitions on the transfer and blending of RBOB. Section 80.69(a) requires that refiners and importers only transfer RBOB to downstream oxygenate blenders who are registered with EPA under the RFG program or, if to an intermediate owner, with the restriction that such owner transfer the RBOB only to a registered blender. Section 80.69(b) requires downstream oxygenate blenders to add oxygenate in the proper type and amount to all gasoline designated as RBOB.(10/17/94)
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)