The era of free money to finance your new car — those attractive zero-percent loans offered by manufacturers — isn’t over yet, but it may be in the final days.

Prodded by rising interest rates as a result of Federal Reserve Board actions and a desire to wean the buying public from an incentive program born of desperation after the Sept. 11, 2001, terrorist attacks, manufacturers across the board are hoping to reduce the flow of incentives — not just on zero-percent loans but on huge cash rebates as well.

“The auto manufacturers — primarily General Motors — really did a service to the country when they slapped the zero-percent financing on their vehicles after Sept. 11 to jump-start the economy,” says Bruce Belzowski, assistant research scientist at the Office for the Study of Automotive Transportation at the University of Michigan.

“But there comes a point where you say, how much money can we spend on these programs and still be profitable? Only now have they started to dial them down.”

Most manufacturers offer zero-percent loans now on just a few slow-selling models, or have limited the term of the zero-percent loans to just 36 months, which would put the monthly payment higher than most people would want.

Dave Reuter, a Ford spokesman, says that nationwide the company is only offering zero-percent financing on Escape and Focus models, and only for 48 months. Some sales regions, such as Ford’s Southeast sector, have limited zero-percent programs to such SUVs as Expedition, which have seen sales slow as fuel prices have risen.

“We have been able to lower our incentives month by month for the last five months,” says Reuter, who expects the trend to continue.

At General Motors, which has seen its sales decline since the first of the year, zero-percent loans have been offered nationwide for 36-month terms on most of its 2005 models, excluding the new Cobalt compact sedan and such prestige cars as Corvette and the Hummer H2.

“There is still a market for zero percent,” says Deborah Silverman, a GM spokeswoman. “But most buyers are looking for something longer term in a loan. It’s a payment issue.”

She says the zero-percent program was scheduled to run only through the end of March.

Regardless, even at its peak the promise of zero-percent loans was, for many buyers, hard to come by.

Most manufacturers, using their finance subsidiaries, have set a fairly high credit rating bar to qualify for the free money. A credit score of more than 700 — which means no blemishes at all on your credit report — has typically been required.

So, many buyers who went to dealers expecting to get a zero-percent loan went home instead with a payment carrying interest, often for 60 months. That helps explain why most manufacturers reported last year that their finance subsidiaries posted substantial profits.

But for buyers who do qualify, will there still be a zero-percent option available when they hit showrooms this spring and summer?

It depends on how well automobile sales are overall, and what happens to interest rates. “When the Fed increases costs, there’s a trickle-down cost,” says Ford’s Reuter.

Belzowski says he believes manufacturers will try to resist a new expansion of zero-percent loans and change the mindset of consumers who may have come to expect such deals. “They have to weather the storm, and I think they are trying to do that,” he says.

But Belzowski also believes that if automobile loan rates do increase substantially, manufacturers may go back to an old sales tool — the low-payment lease.

Currently, leasing accounts for only about 18 percent of all new-vehicles sales, down from a high in the late 1990s of more than 30 percent. “If interest rates continue to rise, leasing will come more into play,” Belzowski says.

What’s the bottom line for consumers? There’s always a deal cooking.

“There will always be something,” Belzowski says. “That’s part of the hook. The consumer just has to decide what the best hook is for them.”