; and (2) by adding at the end the following: (w) Clean octane standard (1) Definitions In this subsection: (A) Baseline lifecycle greenhouse gas emissions The term baseline lifecycle greenhouse gas emissions means the average lifecycle greenhouse gas emissions, as determined by the Administrator, in consultation with the Director of the Argonne National Laboratory, for unblended gasoline sold or distributed as transportation fuel in 2023. (B) Lifecycle greenhouse gas emissions The term lifecycle greenhouse gas emissions means the aggregate quantity of greenhouse gas emissions as determined by the Secretary of Energy using the most recent version of the Argonne National Laboratory Greenhouse gases, Regulated Emissions, and Energy use in Technologies (GREET) model. (C) Research octane number The term research octane number has the meaning given the term in section 201 of the Petroleum Marketing Practices Act ( 15 U.S.C. 2821 ). (2) Aromatics (A) Annual average limitation Effective beginning on January 1, 2027, it shall be unlawful for refiners or importers to sell motor vehicle gasoline that contains, on an average annual basis, an aromatic hydrocarbon concentration in excess of 17.5 percent by volume. (B) 2027 cap Effective beginning on January 1, 2027, it shall be unlawful for refiners or importers to sell motor vehicle gasoline that contains an aromatic hydrocarbon concentration in excess of 30 percent by volume. (C) 2032 cap Effective beginning on January 1, 2032, it shall be unlawful for refiners or importers to sell motor vehicle gasoline that contains an aromatic hydrocarbon content in excess of 25 percent by volume. (D) Oxygenate adjustment for gasoline blendstock (i) In general For purposes of compliance with this paragraph, the aromatics volume of motor vehicle gasoline produced as blendstock for oxygenate blending may be adjusted based on the specified type and amount of oxygenate required to be added downstream. (ii) Requirements Any adjustment under clause (i) shall be made through— (I) the