Because of concern about global warming and American reliance on increasingly costly oil imports, Congress is taking a fresh look at requiring auto makers to boost fuel economy. For the first time in 16 years, federal lawmakers are debating whether to force manufacturers to improve the average mileage-per-gallon performance of new vehicles.

A Senate committee voted unanimously last week to raise the fuel efficiency standard for passenger vehicles by about 40 percent by 2020 -- the first such bill sent to the full Senate since 1991. This time the bill enjoys broader support as Congress tries to curb carbon dioxide, a global-warming gas produced when fossil fuels such as gasoline are burned.

The Senate bill would raise the fuel standard for passenger vehicles to 35 miles per gallon by 2020 from the current 25 mpg. The bill also mandates a 4-percent yearly increase in mileage for medium- and heavy-duty trucks.

Detroit's Big Three auto makers warn against further burdening them with costs by targeting their best-selling pickup trucks and SUVs at a time when they're struggling to survive.

Impact on drivers: Buyers would pay about $1,100 more for new cars, but would recover that amount within five years if gas prices are $2 a gallon and sooner if gas prices increase.

Backer says: "It's been 30 years since Congress really did anything effective for consumers at the pump. And the industry has refused to respond consistently, to its own great detriment."� -- Philip Clapp, president of the National Environmental Trust

Critic says: The idea is "like trying to combat obesity by forcing clothing manufacturers to manufacture only small sizes. It's doomed to failure." -- Bob Lutz, General Motors vice chairman