While Mercedes-Benz has focused its first green marketing efforts on the undeniably impressive 2010 Mercedes-Benz S400 Hybrid, it was joined by a second hybrid Benz that went on sale earlier this month after previewing in April at the New York Auto Show.

The 2010 Mercedes-Benz ML450 Hybrid brings better fuel efficiency to its popular line of ML sport utility vehicles. With a Bluetec clean diesel version already in the lineup, the ML is one of the few vehicles in the U.S. to offer gasoline, hybrid, and diesel variants.

Fuel efficiency over performance

Mercedes-Benz uses its version of the Two-Mode Hybrid system to maximize fuel economy rather than improving performance, as BMW does with a similar system in its 2010 BMW ActiveHybrid X6.

Mercedes-Benz fits its hybrid transmission to a 275-horsepower 3.5-liter V-6. Combined power among the engine and two electric motors is 340 horsepower, roughly similar to the ML550 version powered by a gasoline V-8 engine.

Mileage: 50 percent better than V-8 version

The result is EPA mileage ratings of 21 mpg city / 24 mpg highway, almost half again as good as that V-8 model.

That's also far better than the 17 mpg city / 19 mpg highway ratings of the ActiveHybrid X6, which mates its hybrid to a twin-turbo 4.4-liter V-8 engine putting out 407 horsepower.

Low-speed electric running

The company says the ML450 Hybrid can drive up to 34 miles per hour solely on electric power, though that requires gentle acceleration on level surfaces. On hard acceleration, the gasoline engine restarts, as it does at higher speeds.

The electric motors are powered by a liquid-cooled nickel-metal-hydride battery pack under the rear load deck.

Lease only, no sales

Mercedes-Benz says it will only offer the ML450 Hybrid on three- and five-year leases; it is not available for purchase. The 36-month lease is $659 per month, while the 60-month contract runs $549 a month.

To us, the lease-only option confirms the suggestion that Mercedes-Benz may move away from using the Two-Mode over the long term, in favor of in-house mild-hybrid technology it developed (also with BMW) for the S400 Hybrid sedan. That system features a lithium-ion battery pack, making it the world's first hybrid in volume production to use lithium cells.

GM, Daimler, Chrysler, BMW

The system in the ML450 Hybrid uses similar components and much of the software of the Two-Mode Hybrid system jointly developed starting in 2004 by General Motors, Daimler, Chrysler, and BMW.

But the ML450's system is packaged differently, and very different in feel, from the version found in such workaday vehicles as the full-size 2009 Chevrolet Silverado Hybrid and GMC Sierra Hybrid pickup trucks, as well as GM's large hybrid SUVs (the Chevrolet Tahoe Hybrid, GMC Yukon Hybrid, and full-bling Cadillac Escalade Hybrid).

But built in Germany

The Two-Mode versions from Mercedes-Benz and BMW are substantially different from the ones used in sport utilities and pickups from General Motors and Chrysler.

The housing is shaped differently, for one thing, since the six- and seven-speed automatic transmissions used by the two German makers are longer and narrower than their equivalents in GM trucks. The German version is built for both companies by Mercedes-Benz in a Stuttgart factory, rather than in Cincinnati, Ohio, where the GM and Chrysler versions originate.

2010 mercedes benz ml450 hybrid 004

2010 mercedes benz ml450 hybrid 004

[Mercedes-Benz via TheCarConnection]