Detroit Auto Show: Mercedes-Benz E300 BlueTec Hybrid January 9, 2012, 9:25 am Shown on Monday, Jan. 9: Mercedes-Benz E300 BlueTec Hybrid. An E-Class sedan with a diesel-electric hybrid powertrain. It was presented along with the E400 Hybrid, a gasoline-electric hybrid. There's nothing conceptual about the German brand's first diesel-hybrid sedan, although Daimler, the parent of Mercedes, has not confirmed its prospects for sale outside of Europe. What they said: In a news release, Mercedes-Benz called its new fuel-frugal E-Class "the most economical luxury sedan in the world," but the world in which Mercedes states such things does not include the United States, at least for the time being. The automaker says the sedan is capable of going 100 kilometers on 4.2 liters of diesel fuel, working out to 56 miles per gallon. Top speed is said to be 150 miles per hour, and the automaker estimates a zero-to-60 acceleration time of 7.5 seconds. What they didn't say: While the gasoline-electric E400 Hybrid is a definite for American showrooms later this year, Mercedes is being coy about the future, or lack thereof, of the E300 hybrid in the United States. But given the availability of various BlueTec diesels at American dealerships, as well as the automaker's substantial investment in making these powertrains meet federal emissions requirements, Mercedes would be missing an opportunity to be the only major automaker offering a diesel-electric powertrain in the United States. There's also the matter of Mercedes showing the BlueTec Hybrid in Detroit, not Frankfurt. A 201-horsepower 4-cylinder diesel engine is coupled with a 27-horsepower electric motor and lithium-ion battery. A stop-start function and regenerative braking also contribute to the car's fuel efficiency. The electric motor is contained within the 7-speed transmission's torque converter. Mercedes describes this powertrain configuration as a "modular concept," meaning that it can readily be adapted to other vehicles in its stable. In this segment, fuel economy seldom translates to purchasing economy. But given the premium tags affixed to diesels and hybrids, the price of a premium diesel hybrid might well elicit gasps. Every bit as reserved and precise as the gas-burner on which it was based.