WASHINGTON - The most common deals under the government's $3 billion Cash for Clunkers program, aimed at putting more fuel-efficient cars on the road, replaced old Ford or Chevrolet pickups with new ones that got only marginally better gas mileage, according to an analysis of new federal data by The .

The single most common swap - which occurred more than 8,200 times - involved Ford F150 pickup owners who took advantage of a government rebate to trade their old trucks for new Ford F150s. They were 17 times more likely to buy a new F150 than, say, a Toyota Prius. The fuel economy for the new trucks ranged from 15 mpg to 17 mpg based on engine size and other factors, an improvement of just 1 mpg to 3 mpg over the clunkers.