The fuel efficiency gains helped sway Democrats Dianne Feinstein of California and Chuck Schumer of New York, and Republican Susan Collins of Maine, who had complained that smaller rebates of $3,500 were going to people buying new cars that get as little as 4 more miles per gallon than the gas-guzzlers they traded in.
The three said administration officials told them an additional 100,000 to 130,000 were expected to be processed to reach the $1 billion set aside. The additional $2 billion was expected to generate sales of perhaps a half-million more vehicles.
Car companies said the clunkers program was helping their bottom lines. Ford said its sales rose 2.4% in July from the same month last year, its first year-over-year increase since November 2007, while Chrysler posted a smaller year-over-year sales drop compared with recent months, helped by "clunkers" deals. Other automakers showed gains, giving ammunition to supporters of the car rebate program.
The Ford Focus is a leading replacement vehicle. General Motors, Chrysler and Ford accounted for 47% of the new vehicles purchased.
Most consumers are buying smaller, more fuel efficient vehicles under the program, according to a list of the top-10 selling cars released by the National Highway Traffic Safety Administration, which is administering cash for clunkers.
That includes Honda Civics, Toyota Corollas and Dodge Calibers. The Toyota Prius hybrid, which gets 46 miles per gallon according to EPA estimates, is the fourth best-selling car. There is one SUV on the list, the Ford Escape, which also comes in a hybrid model that can get up to 32 miles per gallon.
Many Republicans remained skeptical, raising objections to the additional costs amid questions about the management of the overwhelmed car rebate program. The GOP holdouts said the government has failed to provide enough data about how well the initial funding has worked and should wait until the fall to provide more.
Many dealers said they were concerned they could be on the hook for some of the money if the Senate fails to act. John McEleney, chairman of the National Automobile Dealers Association, said his organization was warning dealers there were no guarantees they would be reimbursed for sales they make under the program this week. McEleney said he has stopped offering cash-for-clunkers deals at his own Iowa dealerships.
But dealers are still trying to lock up more money. NADA and the American International Automobile Dealers contacted thousands of dealerships, telling them to bombard the Senate with phone calls and e-mails.
Car dealers typically support Republicans and are a potent political force, contributing more than $9 million to federal candidates for the 2008 elections.
Associated Press writers Stephen Manning and Joan Lowy in Washington and Tom Krisher in Detroit contributed to this report.