Clean Fuels Vehicle Act of 2021 This bill allows a new business-related tax credit through 2031 for the production of flexible fuel vehicles (i.e., motor vehicles engineered and designed to be operated on a petroleum fuel and on a methanol or ethanol fuel, or on any mixtures of such fuels). The amount of such credit in a taxable year is equal to the product of $200, and the number of vehicles produced and sold by the taxpayer to an unrelated person in the United States. The bill also repeals limitations on manufacturing incentives for dual fuel automobiles and repeals the maximum fuel economy increase for alternative fuel automobiles.