The 2007 Mercedes-Benz Ocean Drive concept suggests the company is preparing to unveil the four-door convertible by 2011.

Consumer Guide's Impressions of the 2011 Mercedes-Benz Ocean Drive

Mercedes-Benz seems ready to add a four-door convertible based on its big S-Class sedan. It should be much like the recent Ocean Drive concept except in name. Bring big money.

What We Know About the 2011 Mercedes-Benz Ocean Drive

It's tough making a profit in the car business these days, and even top-of-the-market outfits like Mercedes-Benz don't have money to waste on pipe-dream projects. That's why observers took note when Mercedes unveiled the Ocean Drive four-door convertible concept at the 2007 Detroit Auto Show. Though obviously based on the company's big S-Class sedan, the Ocean Drive surely cost a mint to build, which implies it's really a prototype for yet another addition to the ever-expanding Mercedes lineup.

A company press release tacitly confirmed that view by describing the Ocean Drive as a "unique luxury convertible design study [that] turns a 'dream car' vision into reality." Note the word vision. Several recent new Mercedes models have been previewed as thinly disguised "Vision" concepts. Though the Ocean Drive lacks that label, we take the press-release wording as a strong clue that you'll be able to buy something very much like it.

The concept sure looked showroom-ready, but we're guessing that Mercedes will hold the production version to model-year 2011, if only to spotlight an expected mid-cycle freshening for the S-Class line, which was redesigned this year. Because the Ocean Drive name doesn't fit Mercedes' labeling scheme, expect a more prosaic title like "S550 CS," for "Cabriolet Sedan" or maybe S550 SC.

As always with Mercedes, the number on the badge will relate to engine size. The concept was based on the lush S600 sedan and its 510-horsepower turbocharged 6.0-liter V-12, but Mercedes would probably also offer an S550 version with a normally aspirated 5.5-liter V-8 tuned for around 400 horsepower. Hey, even plutocrats need something to aspire to.

The Ocean Drive is much like its sedan parent in looks and size, but wears completely unique body panels-in high-tech carbon-fiber, no less-that some see as forecasting a 2011 S-Class facelift. The main changes from current big-Mercedes styling-besides the drop-top configuration-are an extended nose with larger headlamp clusters and a bolder, V-shaped grille, plus a tidier tail with a subtle new taper to it. High-tech LEDs are the external light source front and rear. Inside are four individual seats with Mercedes' neck-level "air scarf" heating vents, as used on the sporty SL two-seater, plus lots of genuine maple trim. The wood even adorns the solid top cover behind the cockpit, a nod to the available teak decking on the new $335,000 Rolls-Royce Phantom Drophead. These features could well carry over to the showroom model. Ditto a subtle tone-on-tone paint treatment (gold on the concept).

In other respects, Mercedes' four-door convertible vision is quite orthodox. Even the roof design is nothing special apart from its sheer size and hefty padded construction. Like other ragtops, it powers in and out of a covered well. Mercedes makes no claims about how fast the top works. The company is also tellingly silent on structural rigidity, which is difficult to make acceptable even in two-door convertibles, especially big ones.

But engineers know a lot more than they did 40 years ago, which was the last time anyone offered an open-air four-door-a Lincoln Continental you might recall. Sensibly, Mercedes chose not to emulate the Lincoln's rear-hinged back doors, because that compromises rigidity, not to mention side-impact protection. Instead, you find good old front-hinged rear doors, though anchored on stubby B-pillars to leave a big, wide opening with the side windows lowered.

Because of its parentage, Mercedes' Cabriolet Sedan will have a lot in common with S-Class sedans. That means a seven-speed automatic transmission and other standard equipment like an auto-adjusting air-ride suspension, ABS, antiskid/traction control, Mercedes' PreSafe crash-protection system, plus the expected plethora of optional luxury-class gadgets. A few new goodies may be exclusive to the convertible, though it's hard to say now what they might be. Perhaps a rain sensor that automatically raises the top before the interior gets wet? We wouldn't be surprised.

The Ocean Drive concept is based on the Mercedes-Benz S-class sedan.

A Notable Feature of the 2011 Mercedes-Benz Ocean Drive

As a concept, the Ocean Drive had several gimmicks designed to grab attention, such as flush exterior door handles that automatically pop out when touched, a twin-screen rear DVD system, and a chilled compartment sized for a champagne bottle and two stainless-steel flutes. None of these items are so far out that they couldn't be offered on a production basis, though Mercedes accountants and engineers may have other ideas.

Buying Advice for the 2011 Mercedes-Benz Ocean Drive

It's safe to say that you'll need a little patience and lots of money to buy this Mercedes. Nobody else is known to have an open-air four-door in the works, and Mercedes will likely set price high and production low to insure maximum exclusivity and snob appeal.

2011 Mercedes-Benz Ocean Drive Release Date: It's anything but clear at this early point, but sales could begin by fall 2010, assuming a 2011-model launch.

First Test Drive: Again assuming a 2011-model timetable, media previews should be scheduled for the spring or early summer of 2010.

2011 Mercedes-Benz Ocean Drive Prices: We're talking about a convertible version of the Mercedes brand's flagship sedan, so prices should be well into six-figure territory even for a "starter" V-8 model. We'd expect that to run around $150,000, with a V-12 model approaching $200K depending on engine tune and other equipment. That compares with today's costliest S-Class sedans: the $140,000 S600 and the $182,000 high-performance S65.

For more inside information on hundreds of new cars of today and tomorrow, check out:

• Consumer Guide New Car Reviews and Prices: Road test results, photos, specifications, and prices for hundreds of new cars, trucks, minivans, and SUVs from the Auto Editors of Consumer Guide.
• 2007 Mercedes-Benz S-Class: Read Consumer Guide's full report, including ratings, prices, specifications, and fuel economy.
• Premium sporty performance cars: The Mercedes-Benz Ocean Drive will compete in the premium sporty performance car class. Here's Consumer Guide's roundup of all the sporty performance cars on sale today.
• Fuel-economy leaders: The EPA admits its fuel economy numbers are estimates. Ours are real. Here are the fuel-economy leaders as determined in Consumer Guide tests.
• Future Cars: Check out what's just on the horizon.