Environmental groups and many Democrats have long called for sharply higher mileage requirements on new vehicles as the only real way to rein in US oil consumption and reduce crude imports. In March, former Republican national security and defense officials also urged the Bush administration to boost fuel standards.

After years of resistance from automakers, NHTSA raised the the Corporate Average Fuel Economy standard of 20.7 miles per gallon in 2004 to 21 mpg for the model year 2005, 21.6 mpg for 2006, and 22.2 mpg for 2007.

NHTSA estimated the increase would save 3.6 billion gallons of gasoline over the 25-year life of the affected vehicles from the three model years. With one barrel holding 42 gallons, it means the fuel savings will average about 9,400 barrels per day during the 25-year period.

That amount barely stirs the surface of the current 20.9 million barrels of oil a day consumed by the United States.

However, the White House has offered a much brighter picture of the potential fuel savings.

"We've taken some action when it comes to the Corporate Average Fuel Economy standards for SUVs and trucks," White House spokesman Scott McClellan said at an April 13 press briefing. "And, as a result, by 2007, you're going to see some -- see us save some 340,000 barrels of oil a day."

One week later, McClellan repeated the statement.

"We've moved forward on improving the fuel economy standard for SUVs and pickup trucks. And I think in 2007 it's projected that that will reduce the amount of oil being consumed by 340,000-some barrels when that is fully in effect," he told reporters at an April 20 briefing.

What's behind the numbers?

The White House, faced with a slide in the president's approval ratings as US retail gasoline prices rise, based its calculation of the fuel savings for vehicle model years through 2016 that may be adopted when Bush is no longer in office.

The White House used analysis from the Energy Department's Energy Information Administration to come up with the bigger 340,000 bpd number.

McClellan acknowledged in an interview that the amount of fuel saved with the new vehicle standards for just the model years 2005, 2006 and 2007, as estimated by the the NHTSA, would average about 9,400 bpd when fully implemented.

But he said the administration expects at least similar fuel savings for vehicles produced in the model years 2008 through 2016. However, the Transportation Department has yet to issue new fuel standards past the 2007 model year.

"I don't think anyone expects they're going to get lower," said McClellan.

NHTSA said it measures oil savings only for fuel efficiency standards it has approved.