Every other year, Mercedes-Benz unveils a "Vision" concept car at the Frankfurt Motor Show that points the way to cars it will launch in future years.
This year's concept car looks just like a standard 2010 Mercedes-Benz S-Class. Instead, it's the mechanical parts that are remarkable: It's a plug-in hybrid electric vehicle.
S-Class plug-in hybrid
Two years ago, the breathtaking, audacious Vision F700 concept showed how a four-door sedan could offer the performance of a full-size S-Class, more interior room, and the fuel economy of a Toyota Prius.
The F700 used a tiny, advanced 1.8-liter four-cylinder engine that combined elements of gasoline and diesel combustion, mated to a mild-hybrid system.
This year, the Vision S500 Concept is Mercedes-Benz's second plug-in hybrid concept, following the compact E-Cell Plus concept from the Detroit Auto Show.
Claim: 73.5 mpg
The Vision S500 is a plug-in hybrid with a range of up to 18.5 miles on pure electric power, powered by a 10-kilowatt-hour lithium-ion battery pack.
After that, an unspecified V6 engine combines with a 60-horsepower (44-kilowatt) electric motor to operate as a conventional hybrid. The company claims CO2 emissions of 74 grams/kilometer and fuel economy of 73.5 miles per gallon.
(As with all plug-in hybrids, the fuel efficiency real drivers would get depends entirely on how the car is used. This applies to GM's projection of 230 mpg on the city cycle for its 2011 Chevrolet Volt, and to the 67-mpg claim for the 2010 Fisker Karma under a wholly different method.)
Full size car, compact thirst
The concept, whose full name is the 2009 Mercedes-Benz Vision S500 Plug-In Hybrid Concept, phew, "offers superior driving performance while at the same time consuming less fuel than current compacts," in the words of Mercedes-Benz CEO Dieter Zetsche.
The concept is said to deliver acceleration of 0 to 62 mph in 5.5 seconds.