For car buyers, four words mean the difference between going home in a new sedan or their old clunker: Your loan is approved.

They are being uttered more often these days, spurred by a trillion-dollar government program that provides guarantees when those loans are sold to investors. That is helping banks, credit unions and auto finance companies make auto loans at a quickening pace. And consumers are paying less to borrow. Interest rates have been at record lows since last December.

It's bit of good news for the auto industry in the U.S., where 2009 sales are expected to hit a 30-year low of around 10 million when figures are announced Tuesday. Partly because of loosening credit, industry analysts expect more than 1 million cars and light trucks to be sold in December, the best monthly performance since Cash for Clunkers in August.

Financial firms wrote 5.5 percent more car loans in the third quarter compared with the prior three months, Experian Automotive says. Fourth-quarter figures aren't yet available, but Jesse Toprak, vice president of the auto pricing tracker TrueCar Inc., says December saw an uptick in auto loan approvals for consumers with average or above-average credit as auto finance companies tried to clear out inventory.

Paul Taylor, chief economist for the National Auto Dealers Association, said used-car prices also have stabilized due to limited supply, making used-car loans more attractive to banks.

Still, Toprak said it could take another year or even longer for financial firms to trust consumers enough to return to normal levels for auto lending. It's also far from the freewheeling days of the credit boom. Third-quarter auto lending was down 30 percent from the same period in 2006, a year when U.S. car and light truck sales reached 16.5 million.

In the meantime, only those with good credit need apply.

A top-tier borrower _ someone with a credit score between 720 and 850 _ can get a 36-month auto loan with an average monthly rate of 5.74 percent, down from 6.65 percent a year ago, according to Informa Research Services, a financial research firm headquartered in Calabasas, Calif. On a $20,000 car loan, that's a savings of nearly $300 over three years.

But the cost of borrowing has risen for people in the bottom tier. A person with a score of 500 to 589 has seen the average rate climb to 18.56 percent from 16.47 percent a year ago. That translates to an extra $751.68 over 3 years. Banks are still nervous about loaning money to risky borrowers given high rates of unemployment, foreclosures and late payments since the financial crisis began.