Clean Diesel Act of 2003 - Requires the Administrator of the Environmental Protection Agency (Administrator of EPA) to promulgate regulations applicable to motor vehicle diesel fuel produced or imported by any refiner or importer beginning on January 1, 2011.
Sets forth standards for: (1) sulfur content; (2) cetane number; (3) aromatic content; and (4) lubricity level.
Exempts from such standards certain motor vehicle diesel fuel designated for export outside the United States.
Authorizes the Administrator to waive such standards upon petition by one or more States.
Establishes civil penalties and injunctive authority for misfueling practices which knowingly introduce, or cause or allow to be introduced, fuel other than clean diesel fuel into any motor vehicle designed to operate with diesel fuel.
Directs the Secretary of Energy to determine credit amounts for the clean diesel motor vehicle credit and the lifetime fuel savings credit under the Internal Revenue Code in amounts which the Secretary determines will provide appropriate incentives to encourage the widespread consumer acceptance of clean diesel motor vehicles.
Amends the Internal Revenue Code to establish such credits, as well as a credit for producing low sulfur content diesel fuel. Provides for expensing the capital costs incurred in complying with EPA sulfur regulations.
Authorizes the Secretary of Commerce to award grants to States and cities to convert old plants to produce clean diesel motor vehicles.