; and (2) be blended by adding sources of octane value that meet the requirements of subsection (c) to the low-level ethanol-gasoline blend test fuel used to certify model year 2020 light-duty vehicles. (c) Low-Carbon requirement In carrying out subsection (a), the Administrator of the Environmental Protection Agency shall ensure that the sources of octane value for the certification test fuel allowed under subsection (a) have average lifecycle greenhouse gas emissions, as determined by the Secretary of Energy using the version of the Argonne National Laboratory Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model in effect as of the date of enactment of this Act, that are at least 30 percent less than the baseline lifecycle greenhouse gas emissions. (d) Definitions In this section: (1) Baseline lifecycle greenhouse gas emissions The term baseline lifecycle greenhouse gas emissions means the average lifecycle greenhouse gas emissions, as determined by the Administrator of the Environmental Protection Agency in consultation with the Director of the Argonne National Laboratory, for unblended gasoline sold or distributed as transportation fuel in 2018. (2) Lifecycle greenhouse gas emissions The term lifecycle greenhouse gas emissions means the aggregate quantity of greenhouse gas emissions as determined by using the version of the Argonne National Laboratory Greenhouse gases, Regulated Emissions, and Energy use in Transportation (GREET) model as in effect on the date of enactment of this Act. (3) Light-duty vehicle The term light-duty vehicle has the meaning given to that term in section 216 of the Clean Air Act ( 42 U.S.C. 7550 ). (4) Research octane number The term research octane number has the meaning given such term in section 201 of the Petroleum Marketing Practices Act. 102. Clean octane standard (a) Requirements Section 211 of the Clean Air Act ( 42 U.S.C. 7545 ) is amended— (1) in subsection (d)(1), by striking or (o) and inserting (o), or (w)