An oxygenate blender "certifies" RFG produced by combining RBOB with oxygenate by adding the proper type and amount of oxygenate. In the case of an oxygenate blender who meets the oxygenate standard on a per-gallon basis, the oxygenate blender is not required to sample and test each batch, but rather to conduct a specified quality assurance program of sampling and testing.
The oxygenate blending records would be sufficient to "certify" that a particular batch that is not tested was properly blended. In the case of an oxygenate blender who meets the oxygenate standard on average, every batch must be certified by sampling and testing.
The RFG regulation does not specify the distance or length of time that a batch must be transported in the delivery truck before proper mixing occurs. In order to ensure that proper mixing has occurred, the driver should sample the batch immediately before he places it in the underground storage tank at the retail station or when the batch reaches its final destination.(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)