NEW YORK (CNNMoney.com) -- The PT Cruiser has been a huge hit for Chrysler. Now, the company wants to make sure it stays that way, even as the car enters its eighth year and Chrysler executives wrestle with the big question: What should an all-new PT Cruiser look like?

The PT Cruiser doesn't sell at prices way over sticker like it did when it debuted in 2000, but it's still selling well - more than a million have been sold over the years.

2006 Chrysler PT Cruiser

The PT Cruiser has the advantages of a cool retro look along with a space-efficient shape that makes it a practical and fuel-efficient alternative to a small SUV.

"The PT remains one of the few iconic cars that is really useful in everyday life," said David Zatz, who runs the Web site Allpar.com, devoted to current and past Chrysler products.

The Cruiser's look was originally borrowed from the Plymouth Prowler, a hot-rod-styled two-seat convertible that debuted in 1997. At the time, Chrysler's Plymouth brand was moving toward a style harkening back to its earliest years in the 1930s. (The Plymouth marque was created in 1928 as Chrysler's lower-priced alternative.)

By 2001, following the merger with Daimler-Benz, Plymouth was dead. So the PT Cruiser, with its depression-era look, was introduced as a Chrysler instead.

Now, according to reports in two industry newspapers, Chrysler is struggling about what comes next.

The Cruiser did get a facelift for the 2006 model year, but the differences are so mild that only serious Cruiser fans would notice them. So, it's getting to be a long time without a major redesign and, in the car industry, that just won't do.

Where to now?

Chrysler executives are looking at a new PT Cruiser, possibly for the 2008 model year, according to WardsAuto.com. Automotive News puts the date at 2009 or '10.

But it won't be easy.

"You have a retro vehicle - and how do you update a retro vehicle?" Frank Klegon, executive vice president for product development, told the auto industry news site WardsAuto.com.

Good question.

Even experts can't think of a single retro-themed car that has ever been substantially redesigned. Retro design can be a trap because it relies on very specific visual cues to evoke a strong emotional response. Messing with those cues could lead to an equally strong rejection.

"Will they attack all the things people pick out as problems and sandpaper off all the edges until there's nothing?" worried Zatz.

Part of the Cruisers character is its small size. It's built on a modified form of the now defunct Dodge Neon's small car platform.

But Chrysler might opt to make the new PT Cruiser substantially larger, according to the reports. That might mean sharing its underlying structure with the redesigned Chrysler Sebring, Klegon told WardsAuto.com.

That would provide the possibility of offering a V-6 engine, Chrysler Chief Operating Officer Eric Ridenour told Automotive News. That would answer critics' complaints that the PT Cruiser, particularly with its base engine, is too slow.

A larger PT Cruiser with a V-6 engine would also fit better into the Chrysler brand's renewed focus as a luxury marque, said Mike Jackson of the auto marketing consultancy CSM Automotive.

"They can move it upmarket a little bit," he said.

Another, and possibly cheaper, solution would be "badge engineering" the just-introduced Dodge Caliber. In the same way that the Dodge Charger is essentially the same vehicle, underneath its body, as the Chrysler 300, the new PT Cruiser could be a retro-themed version of the Caliber.

The Caliber has roughly the same size and shape as the PT Cruiser, although the cars share no engineering. The Caliber is available with all-wheel-drive and it's offered with a fuel-efficient continuously variable transmission.

The Caliber suffers from the same criticism as the Cruiser when it comes to power, though. The Caliber, even in its supposedly performance-oriented R/T trim level, feels slow.

But with gas prices rising, introducing a bigger Cruiser with a V-6 engine might be an ill-timed move, suggested Jim Hossick of AutoPacific.

"A year ago I would have said America would really rather have a six than the four," he said.

With gasoline prices topping $3 a gallon, Americans want smaller engines and better mileage, he said.

No final decision has been made, Chrysler executives told the newspaper.

Zatz isn't buying that, though. By this time, they know the fundamentals of the next Cruiser and all this industry talk is just a shell game to keep competitors and Chrysler-watchers like him guessing, he said.

Chrysler executives declined to comment for this story.