Green cars from the Frankfurt Motor Show

This big Mercedes-Benz luxury sedan combines a fuel efficient 4-cylinder clean-diesel engine with a hybrid electric motor for a combined 224 horsepower.

The car would get about 44 miles per gallon, according to Mercedes-Benz and could meet the most stringent European and U.S. emissions standards.

Mercedes-Benz also unveiled the more powerful S400, which uses a V6 gasoline engine. It should get almost 30 miles per gallon, according to Mercedes-Benz.

Mercedes also unveiled a highly fuel efficient luxury sedan concept vehicle, called the F700, that uses a new type of internal combustion engine.