Green is all the rage at this year’s Frankfurt International Motor Show, Sept. 13 – 23. The automakers are casting bright lights on their hybrids, plug-in hybrids, clean diesels, fuel cells, and other advanced vehicles. But the glare of publicity makes it difficult to distinguish between the vehicles headed to a showroom in the next few years—and those with delivery dates somewhere between 2015 and never. We look at the vehicle unveilings in Frankfurt and give our ratings: Coming Soon, Way Out, or Maybe Never.

Coming Soon

The first public glimpse of BMW’s X6 is the hybrid version. The X6 ActiveHybrid, labeled as a “sport activity coupe,” utilizes the two-mode hybrid system that BMW jointly-developed with General Motors and DaimlerChrysler. Fuel economy is estimated at roughly 30 mpg, which is 20 percent higher than the conventional version. Sales of the non-hybrid X6 will begin in the United States next summer. BMW didn’t comment on timing for the X6 ActiveHybrid. If released in 2009, the X6 Hybrid would become first full hybrid in the BMW lineup.

Mercedes-Benz revealed a full line of hybrids at the Frankfurt show. The two vehicles first set to launch are the S400 Hybrid—a mild-hybrid S Class—and the ML 450 Hybrid using the two-mode system. The vehicles, both targeted at about 30 mpg, will threaten Lexus’s exclusive position in the niche luxury hybrid market when they hit American showrooms sometime in 2009.

Way Out

Porsche purists cringed as the company showed off a hybrid version of the Cayenne SUV. The Cayenne will use a robust hybrid drivetrain—co-developed with Volkswagen—to increase fuel economy by 15 percent. Hybrid purists cringed as they learned that the 8-cylinder Cayenne Hybrid’s gas mileage would still be less than 20 mpg. Porsche’s hopeful estimate for launching the Cayenne Hybrid is 2010.

Mercedes-Benz is vying to become the first company to combine a hybrid powertrain with a diesel engine in a production vehicle. The new models include the E300 and S300 BLUETEC Hybrids, based on the E Class and S Class platforms respectively. Both are rated in the range of 45 mpg, and are expected to reach showrooms in approximately five years. The big question regarding diesel hybrids is the cost of doubling up on the two fuel efficiency systems.

Saturn showed a plug-in hybrid version of its redesigned Vue crossover. The plug-in Vue is General Motors’ first scheduled grid-rechargeable hybrid. The vehicle adds plug-in capabilities to the two-mode hybrid system—with the goal of roughly 10 miles of all-electric driving range. Saturn gives an uncertain timetable of “2009-ish” to release the plug-in Vue—but given the challenges of lithium ion batteries, the launch could easily slip to 2010 or 2011 or 2012…

Volve ReCharge

While Volvo says the ReCharge may be feasible to produce in five years, the company would need to make a major shift in direction to bring a plug-in hybrid electric vehicle this quickly to market. The ReCharge is more “me too” concept than reality.

Maybe Never

Attempting to export the buzz for the Chevrolet Volt concept across the pond, General Motors revealed the Opel Flextreme concept—a European version of GM’s E-Flex plug-in series hybrid. This variant uses a diesel engine instead of a gasoline powerplant. According to GM, the Flextreme can drive for roughly 35 miles on battery power alone or for almost 450 miles when electricity from its 1.3-liter diesel generator is used. As with the Volt, the future of the Flextreme depends on affordable, durable, and safe lithium ion batteries. We could all be ten years older and grayer before GM puts a plug-in diesel-hybrid on sale.

Volvo unveiled the ReCharge, its own version of a plug-in series hybrid. The car is based on the company’s compact C30 and promises 60 miles of all-electric range. While Volvo says the ReCharge may be feasible to produce in five years, the company would need to make a major shift in direction to bring a plug-in hybrid electric vehicle this quickly to market. The ReCharge is more “me too” concept than reality.

Mercedes-Benz announced its intentions to sell a limited number of fuel cell vehicles based on its compact B Class car. The big question is how limited is “limited?” While Mercedes-Benz gave 2010 as the ambitious launch date, the challenges with fuel cells and hydrogen infrastructure are well-documented. It could easily take 15 – 20 years for a vehicle like the B Class F-Cell to get produced and sold in quantities beyond a few thousand.