Blendstocks
Blendstocks are petroleum products used for blending or compounding into finished motor gasoline. These include RBOB (reformulated blendstock for oxygenate blending) and CBOB (conventional blendstock for oxygenate blending), but exclude oxygenates, butane, and pentanes plus.
Source
40 CFR § 98.6
Scoping language
All terms used in this part shall have the same meaning given in the Clean Air Act and in this section.