Seeing the commercials this month, you’d think everyone was about to head out to buy a turkey, some cranberry sauce and an upscale midsize SUV with satellite radio and real-time traffic updates. More than a dozen automakers have already rolled out holiday-themed promotions that start before Thanksgiving. Many will run right through New Year’s Day.  

Some of the offers are worth considering – good deals on good cars that, if you’re in the market, might well be your best chance to find new wheels that fit your lifestyle and budget. But some of them aren’t. Some might get you into a frustrating situation with a car that eats a hole in your budget for years.

Below, we’ll run through a few of the enticing incentives you’ll see advertised this season, and the reasons you might want to stay away. We’ll use cost-of-ownership data from the experts at IntelliChoice. They look at everything from expected repair costs to insurance and depreciation. A good value, in their view, is a car that costs less to own and operate than expected over five years, based on its competition. Each of the cars we’ll highlight costs more to own -- sometimes a lot more -- than its competition. In some cases, those extra ownership costs are enough to offset the holiday savings.

2009 Saturn Aura: 0% APR financing for up to 72 months, or $4,000 cash back

Average Paid: $20,710 - $25,160

The Aura was the North American Car of the Year just two years ago, but it hasn’t aged well. It’s still pleasant to drive, with crisp handling for a family car. But IntelliChoice data shows that the Aura costs more to own over a five-year period than nearly anything else in its class. The main reason has little to do with the car itself. It’s depreciation. Saturns have lost value quickly in recent years, as doubts about the company’s future took hold.

Now, its future is certain – General Motors has announced that it’s over for Saturn. Every Saturn dealer will close its doors, or convert to selling something else, by the end of December. That will likely only accelerate depreciation – IntelliChoice calls the Aura a “below average” value, and it’s going to get worse.

Consider Instead: The Hyundai Sonata (average paid: $18,634 - $26,221) is rated an “excellent” value by IntelliChoice, and is available with zero-percent APR financing for up to 60 months or $1,000 cash back this month.

Mazda RX-8: $5,000 Cash Back

Average Paid: $25,423 - $31,101

There are few sports cars that hold a perfect line in a tight corner with the poise and balance of Mazda’s RX-8. With four doors (well, okay, two of them are half doors), it’s nearly the only sports car you can buy that has a back seat you can actually use. And, sadly, it burns money like it burns gasoline. It’s not just a matter of poor fuel economy (though, with an EPA rating of 16 mpg around town, that’s part of the problem). It’s upkeep.

The RX-8’s unique rotary engine burns through oil like nothing else on the market. Mazda actually recommends that owners check the oil every other time they refuel. The rotary engine isn’t something most mechanics can repair easily, and parts aren’t cheap. These costs hurt the car’s long-term value, too. Few people want to buy a second-hand car that will cost them a fortune to maintain. The combination earns it a “poor” value rating from IntelliChoice. Buy one, and you might spend that extra $5,000 in cash at the gas pump and Jiffy Lube.

Consider Instead: The holiday specials don’t extend to any affordable sports cars with above-average IntelliChoice ratings. But if you long for a roadster and have to pay full price, it might be worth paying full price for another Mazda. The MX-5 Miata (average paid: $22,135 - $28,283) tops our affordable sports car ranking list, and IntelliChoice rates it an “above average” value.

Mercury Mountaineer: 0% APR for up to 60 months, or up to $3,000 cash back

Average Paid: $28,015 - $35,136

Mercury’s midsize Mountaineer SUV is cheap this month, with a big cash-back rebate or an interest-free financing offer. With a roomy, quiet cabin, five-star scores in every government crash test, and a tow rating that matches what many larger SUVs can claim, it looks enticing to those who need three rows of seating.

But its long-term value doesn’t look so good. Most SUVs now are crossovers, meaning they are built on car platforms. They’re easier to drive, often more family-friendly, and don’t guzzle fuel like the old truck-based ‘utes. The Mountaineer, however, is still built on the aging Ford Ranger truck platform. It gets just 14 mpg in city driving, and depreciates very quickly. IntelliChoice rates it a “below average” value.

Consider Instead: The Buick Enclave (Average Paid: $34,514 - $42,742) costs more, but lower trim levels compete with the Mountaineer on price. You’ll enjoy driving it, and it will save you over time -- it earns an “excellent” value rating from IntelliChoice. It’s available now with $1,500 cash back.

Jeep Commander: Up to $4,000 cash back

Average Paid: $33,788 - $43,273

Jeep may have built the original Sport Utility Vehicle, but they don’t get it right every time. The largest Jeep product, the Commander, will outperform most large SUVs off road, and does well in government safety tests. But it depreciates faster than a typical full-size SUV, costs more to insure, and costs more to maintain. IntelliChoice rates it a “below average” value in every trim level, except its 4WD Limited edition, which rates “poor.”

Consider Instead: GM’s full-size offering, the Chevy Tahoe (average paid: $36,374 - $51,332) scores an “Excellent” value rating from IntelliChoice, and is available with zero-percent APR financing for up to 72 months until Jan. 4, 2010. Their highest trim levels are more expensive than the Commander, so you’ll have to keep the optional equipment reasonable, but GM’s SUVs hold their value better over time and are cheaper to insure and maintain.

Dodge Ram 1500: Up to $6,000 cash back, or 0% APR financing for up to 72 months plus $1,500 cash back

Average Paid: $20,359 - $40,617

Dodge took a risk in designing the latest Ram, abandoning the traditional leaf-spring suspension that most big trucks use to carry heavy loads. Instead, the Ram offers a coil-over suspension. That means that the Ram offers the most car-like ride of any full-size pickup. But the Ram costs more to insure and maintain than its major competitors from Chevrolet and Ford. It’s the only one of the three domestic-made full-size pickups that fails to earn a “better than average” rating from IntelliChoice. Instead, the Ram earns a “below average” grade.

Consider Instead: The experts at IntelliChoice rate the Chevy Silverado (average paid: $19,321 - $40,124) an “Excellent” value. It is offered with up to 72 months of interest-free financing this holiday season.