Unlike typical Black Friday sales where customers know exactly what they'll pay for an item, car prices are individually negotiated the day of the sale, so it's difficult for customers to know ahead of time they'll be getting a deal. But there's been a clear trend, Toprak said.

The average new car discount on Nov. 27 is projected to be 7.5%. The average discount the day before and after is expected to be just over 6%. On a typical day throughout the year, car shoppers usually pay about 4.7% less than the sticker price.

Truecar.com projected particularly large Black Friday discounts on certain models. For instance, consumers should be able to pay about 28% off sticker price for a 2009 Suzuki SX4 compact car, 26% off for a 2009 Nissan Titan or Ford F-150 pick-up or 20% off a 2009 Hyundai Sonata sedan.

Cash for clunkers is the best-known name for the big government program that began this week to offer $3,500 or $4,500 incentives to owners of old gas guzzling vehicles who trade them in on more fuel-efficient ones. It is intended to spur moribund auto sales, helping both dealers and manufacturers.

But rules governing the program totaled 135 pages. They required dealers to register and many started off the week just trying to get answers on a government-jammed website. The rules are "very confusing," says Pete Greiner, who has a Ford dealership that bears his name in Casper, Wyo. "The administration of the program is extremely tough."

But some dealers say demand has been so brisk, they fear the program could go broke in days or weeks, long before its Nov. 1 expiration.

One Honda and General Motors dealer in Fort Worth says he has 50 clunker deals that are being held up by paperwork. "We're going back to our second and third round with customers to have things signed," says Will Churchill, owner of Frank Kent Motor. "They keep coming up with new forms to sign," Churchill says.

Now the dealership is in a Catch-22 situation: he must destroy the engines of clunker trade-ins to be eligible for the program. But if the paperwork falls through, he could be stuck with junked, rather than still running, cars.

As a result, Churchill says he is thinking of holding up more clunker deals.

Small-car sales doubled during the first half of the year as gas topped $4 a gallon. By the end of November, sales levels had tumbled 63% from the peak. Even with the drop, the segment is holding up better than others because overall vehicle sales are so weak. "It's surprising," says Ford Motor analyst George Pipas.

No other vehicle segment saw such sales volatility in 2008. First, it was falling gas prices that slowed small-car sales. Now, it's the inability of recent college graduates and other price-conscious drivers to qualify for loans. "The credit market is squeezing first-time buyers out. They are getting laid off and being exposed to the economy more than others in their careers," says General Motors spokesman John McDonald.

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With the recession making cars harder to afford, automakers are looking to price-cutting to attract buyers. Nissan struck first in October, offering a new version of its smallest model, the Versa, with a less powerful engine and fewer features. It was priced at $9,990.

It didn't remain the "lowest-priced new car in the U.S.," as Nissan billed it at the time, for long. Hyundai cut the price of its Accent hatchback by $1,775 to $9,970. That's $20 cheaper than the Versa.