If diesels and hybrid cars both get great mileage, why not add a hybrid system to a diesel engine? Mercedes-Benz decided to answer that in the affirmative, showing off numerous diesel-electric hybrids at the 2007 Frankfurt auto show. Because diesel engines and electric motors duplicate their most efficient performance bands, high torque at low RPMs, Mercedes-Benz found a small hybrid system was all that was needed on its Bluetec diesel electrics, rather than the more robust two-mode system coming out on its ML450 and S400.
In 2010, Mercedes-Benz will launch the E300 and the S300, both cars using a Bluetec 2.2-liter four-cylinder diesel engine complemented by a 20-horsepower electric motor. Both cars will also get a seven-speed automatic transmission. The S300 will go from 0 to 62 mph in 8.4 seconds and get 44 mpg. After 2010, Mercedes-Benz has the C300 and the S400 up its sleeve. The C300 will use the same hybrid powertrain as the E300 and S300, but due to its lighter weight, it will go to 62 mph in 7.2 seconds and get 51 mpg. The S400 will use Mercedes-Benz's 3.2-liter turbocharged V-6 diesel and, with its hybrid system, hit 62 mph in 7.3 seconds while getting 41 mpg.