While the top-selling hybrid-powered vehicle remains the 50 mpg Toyota Prius at a modest $23,000, a growing number of upper-premium gas/electric models are available for well-heeled motorists who want to drive a “greener” car that nonetheless remains both posh and powerful. One of the latest entries in this segment is the Mercedes-Benz S400, which applies the hybrid treatment to the automaker’s largest and most luxurious sedan.
The S400 is technically a “mild hybrid” in that a small electric motor/generator is used only to augment a gasoline engine. It never actually drives the car on its own (albeit only briefly and at lower speeds), as is the case with the Prius and other more mechanically complex “full hybrid” models.
Here, the primary means of propulsion is a 3.5-liter V6 gasoline engine that nets a modest 275 horsepower. A 20-horsepower electric motor acts as a high-tech turbocharger, providing additional torque to ensure quick launches and brisk highway passing abilities. Driving the rear wheels via a sophisticated seven-speed automatic transmission, the two power sources make the S400 feel every bit as lively as the conventional S550 version with its 382-horsepower V8 engine.
A compact lithium-ion battery pack recharges itself from energy recovered during deceleration and braking. As in all hybrids, the gasoline engine automatically shuts down when the car comes to a stop, starting up instantaneously when needed; it is through this feature that the S400 realizes much of its fuel economy gains.
The Environmental Protection Agency rates the Mercedes-Benz S400 at 19-city/25-highway mpg, which is tops among large luxury cars. Though it may not seem like a quantum leap over the V8-powered S550’s 15/23 mpg, this amounts to a 27 percent improvement in around-town economy. The EPA estimates a motorist clocking 15,000 miles per year (with premium-grade gas conservatively priced at $3.85 a gallon) will save around $450 annually owning an S400 instead of the S550.
Unlike most other hybrids, which typically carry a price premium over a comparable standard-powered model, the S400 is the least-expensive S-Class version, though it still commands a hefty $91,000. Environmentally conscious buyers will likely care more that the car is responsible for consuming 2.7 fewer barrels of oil and emitting 1.5 fewer tons of greenhouse gases each year than its V8-powered counterpart, according to the EPA.
So why should anyone get excited about a mildly electrified luxury sedan that saves a few miles per gallon and carries a sticker price that can reach well into six figures with options? Because the Mercedes-Benz S400 illustrates how mainstream large and midsize cars in the coming years will be able to maintain acceptable levels of performance while garnering improved fuel economy to meet stricter federal standards.
For example, the 2012 Buick LaCrosse and Regal models feature a new “eAssist” system that teams a 2.4-liter four-cylinder engine with a power-boosting electric motor and further includes an automatic start/stop function. It’s the base powertrain in the updated LaCrosse, just reaching dealer’s showrooms with an MSRP of $29,960, where it’s claimed to achieve 25/37-mpg. That’s on a par with many compact cars. The redesigned 2013 version of the Chevrolet Malibu, coming early next year, will likewise offer its own mild electrification system.
Getting back to the Mercedes-Benz S400, look beyond the hybrid propulsion system and it remains an S-Class to the core. This handsomely cast large sedan lives up to its top-shelf reputation with an effortless driving experience and a cavernous passenger cabin that affords limousine-like rear legroom. It’s not as sporty feeling as its main rival, the BMW 7 Series, but it delivers an abundance of elegance and unparalleled passenger comfort.
Nowhere is this more apparent that with the optional “Drive-Dynamic” multi-contour seats that came with our tester. They’re not only heated and ventilated, but include cushions that automatically adjust to an occupant’s size and weight, and can give a relaxing top-to-bottom kneading massage to make even the most grueling commutes tolerable.
And that’s one feature you definitely won’t find in a Prius.
MSRP: $91,000, not including $875 destination charge.