The Mercedes-Benz S400 Hybrid, above, notifies driver of remaining battery power, below.
Mercedes-Benz has added a hybrid model to its flagship S Class sedan for 2010 and those who can afford one will find that, unlike other hybrids, it involves virtually no compromises in the driving experience.
The S400 Hybrid is essentially the same large sedan as the S550, except that it gets its power from a V-6 engine and a disc-shaped, 20-horsepower electric motor placed between the engine and the seven-speed automatic transmission.
I had the opportunity to spend some time with the S400 during a recent press event and it proved to be the most transparent hybrid I have tried yet.
The only difference a driver notices is that the engine shuts off at stops signs and traffic signals. As soon as the driver moves his foot from the brake, the gasoline engine restarts so seamlessly it basically goes unnoticed.
Unlike the full-hybrid Toyota Prius, the S400 is a “mild” version which does not run on electricity alone. The motor, powered by an industry-first lithium-ion battery pack, is used for starting the engine and boosting power under acceleration. It also acts as a generator to supply electricity to the battery pack when the vehicle is coasting or under braking.
The lithium-ion battery pack is stored under the hood like a conventional lead-acid battery and is kept cool by the car’s air-conditioning system.
The car’s standard 12-volt lead-acid battery, which handles the routine electrical chores, has been moved to the trunk and has a negligible effect on cargo capacity.
The engine’s 275-horsepower V-6 engine is tuned to run on the less powerful, but more frugal Atkinson Cycle. Combined with the motor, the system produces 299 horsepower, enough to propel the large sedan from a stop to 60 mph in 7 seconds.
My time with the S400 was on two-lane rural highways. I particularly appreciated the boost from the electric motor when it came time to pass slow-moving traffic.
I also observed during my first drive that the hybrid’s steering, braking and handling felt nearly identical to that of the big gasoline-powered Benz.
The S400 hybrid has been preliminarily rated by the EPA at 19 mpg city/26 mpg highway. That compares with 15 mpg city/23 mpg highway for the V-8-powered S550 sedan.
However, drivers have reported achieving 29-30 mpg on the highway. Mercedes-Benz estimates that, overall, the hybrid is about 30 percent more fuel efficient than the S550.
Invisible to me, but important for the planet, less fuel consumed means fewer pollutants released into the atmosphere.
The S400 is the least expensive S-Class in the United States. Its base price is $87,950, a saving of more than $5,000 over the S550.
Less-expensive at the dealership, cheaper at the pump, no loss in driving pleasure and better for the environment -- for a well-to-do few that could make a compelling case for hybrid power.
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