To encourage the availability and use of motor vehicles that have improved fuel efficiency, in order to reduce the need to import oil into the United States.

Amends the Internal Revenue Code to: (1) allow a tax credit for 25 percent of the cost of certain automobiles, trucks, or vans with fuel efficiency ratings of not less than 40 miles per gallon (35 percent for ratings of not less than 50 miles per gallon); (2) allow a business tax credit for the manufacture or production in the United States of qualified fuel-efficient automobiles for first retail sale; (3) make permanent the tax credit for increasing research activities; and (4) increase the rates of the alternative incremental tax credit for research activities.

Authorizes the Secretary of Energy to provide loan guarantees up to $100 million per loan (up to $1 billion aggregate) to automobile manufacturers for the cost of converting to automobiles with a fuel efficiency rating of more than 40 miles per gallon.

Prohibits the Administrator of the Environmental Protection Agency (EPA) from considering any automobile allowed a fuel-efficiency tax credit under this Act in calculating the average fuel economy of a manufacturer.