On August 24, 2018, the Environmental Protection Agency (EPA) and National Highway Transportation Authority (NHTSA) issued a proposed rule: the “Safer Affordable Fuel-Efficient (SAFE) Vehicles Rule for Model Years 2021-2026 Passenger Cars and Light Trucks” (SAFE Vehicles Rule).” With the proposed rule, EPA and NHTSA provided a preliminary regulatory impact analysis (henceforth, the PRIA) to quantify its effects. The rule proposes to amend certain existing Corporate Average Fuel Economy and tailpipe carbon dioxide emissions standards for passenger cars and light trucks and establish new standards, all covering model years 2021 through 2026. If finalized, the rule would amend and replace a number of previous requirements that would reduce carbon dioxide emissions. The PRIA assesses the associated economic effects of the rule’s associated forgone climate benefits by employing an updated value for the federal government’s social cost of carbon (SC-CO2), developed under Executive Order 13783. This updated value for the SC-CO2 and the related methodological changes from the federal government’s previous estimation process for the SC-CO2 are the subject of this comment.