2010 Mercedes-Benz S-Class

For 2010, the Mercedes-Benz S-Class bears a slightly stronger resemblance to upscale Maybach sedans than any Mercedes yet. The changes on the 2010 S-Class compared to the 2009 model are subtle but nevertheless change a few exterior details to keep the sedan fresh.

The most notable change is in the rear end, where designers have unified the previously three-tiered taillights into one unit, complete with LEDs. Exhaust pipes are more rectangular, a theme that spreads to the more angular rear view mirrors, as well. In front, LEDs line the bottom of the front fascia while only current Mercedes S-Class owners are likely to notice the tweaked grille and headlights.

It's probably best to call the new 2010 Mercedes-Benz S400 BlueHybrid a mild, rather than full, hybrid, because it can't propel itself on electrical power alone. In other words, the BlueHybrid is not powered by the two-mode system co-developed with GM for big SUVs, which will be an option for the M-Class next year. This is a smaller, cheaper system designed to be scaleable across all Mercedes car lines.

Despite its comparative simplicity, the Mercedes S400 BlueHybrid's gasoline and CO2 savings are significant: some 21% in the European test cycle, compared with the regular V-6 S350. It's also quieter at rest and more muscular in real-world acceleration. There's very little penalty over the standard V-6 in terms of weight -- just 170 lb -- and none at all in passenger or luggage accommodation or payload.

Of course you can't buy a regular Euro-spec S350 in the U.S., so let's do the numbers against a V-8 S550. The BlueHybrid goes 47% farther on a gallon than the S550 on the Euro test cycle, but its performance figures aren't so far off -- about seven sec 0-to-60 instead of 5.4. That's why they called it S400: because it feels like a four-liter engine.

The battery provides up to a 5-sec jolt of juice (limited by the system's heat build-up) to a thin, 20-hp motor that's slotted between the engine and seven-speed automatic transmission in much the same fashion as Honda's familiar Integrated Motor Assist. However, unlike Honda's system, Mercedes' application is truly "mild" as it can't propel the car in EV mode at all. Consider as well that the 2010 Mercedes-Benz S-Class motor's 20 hp is being applied to a 4575-lb sedan, a 9%-higher lb/hp ratio than the Honda Insight's 13 hp in a 2735-lb vehicle. However, also notice that the motor's whopping 118 lb-ft of torque is a disproportionate aid to the 255 lb-ft delivered by the 275-hp, 3.5L, four-valve/cylinder, Atkinson-cycle V-6 (the system's combined horsepower is 295, combined torque is 283 lb-ft). Mercedes openly admits this is a first step in its sedan's hybridization, and additionally it's one that's constrained by the transmission's existing dimensions and the available room in the 2010 Mercedes S-Class's crowded engine bay (no batteries in the trunk, please). By the way, it was whispered that the next generation of electric motors is likely to produce 60 hp. At three times this motor's output, this strongly suggests Mercedes will have to adopt a clutch between the motor and engine to allow pure EV mode. Unlike Honda, which gets away with powerlessly spinning its small-displacement engines, Mercedes' 3.5L is a lot of engine to consider free-milling.

2010 Mercedes-Benz S400 Hybrid The S-class gets a minor update this fall, but the big news is the arrival of the S400 Hybrid, which combines a 3.5-liter V-6 and an electric motor for 295 hp and 284 lb-ft of torque, enough to send this long-wheelbase sedan to 62 mph in 7.2 seconds, yet it delivers 30 mpg (combined) in European testing.

The 2010 Mercedes-Benz S400 BlueHybrid's propulsion system prioritizes low emissions and high fuel efficiency over powerful acceleration. Essentially a scaled-up version of Honda's Integrated Motor Assist, this new Mercedes powertrain teams a 3.5-liter Atkinson-cycle V-6 with a compact AC motor-generator bolted securely to the crankshaft and a ZF seven-speed automatic transmission. The ring-shaped motor-generator is nearly a foot in diameter but less than two inches thick. The Atkinson cycle, a common hybrid technology, uses late closing intake valves to stretch the expansion (power) stroke for utmost efficiency. While some torque is sacrificed with this approach, the 2010 Mercedes S400's electric motor supplies up to 118 lb-ft to more than cover that loss. The S-class's most notable distinction is the hybrid world's first lithium-ion battery system. Thirty-three cylindrical cells supplied by the French firm Saft are housed in steel container mounted under the hood. (The Tesla Roadster is powered solely by lithium-ion batteries with a similar, but smaller, cylindrical configuration.)

Mercedes started with the S350's 3.5-liter V-6 and added an electric motor powered by lithium ion batteries - the first in a production vehicle. The battery pack is small enough to fit in the engine compartment (the conventional battery was moved the trunk), while the 20 hp motor sits between the V-6 and the 7G-Tronic seven-speed automatic transmission. The entire package adds only 165 lbs. Engineers also squeezed more power and efficiency out of the gasoline engine by modifying the valve and camshaft timing while adding new cylinder heads and pistons. The changes net 7 hp, combining with the electric motor to make 299 hp and 284 lb-ft of torque.

In both form and function, the S400 skews toward the mild end of the hybrid spectrum. The electric motor never powers the car by itself, and is tuned to provide more power in addition to economy. Mercedes said the motor adds a "boost" effect during hard acceleration, projecting a 0-62 time of 7.2 seconds and a governed top-speed of 155 mph. Inside, the S400 eschews a prominent hybrid status screen and instead displays the information in the instrument cluster. A stop/start function shuts off the gasoline motor when the vehicle slows to less than 9 mph, and uses the electric motor to ignite the engine again as soon as the driver lets off the brakes. Like most hybrids, the batteries recharge during braking.

The result is a combined fuel economy of roughly 30 mpg, an improvement of about 4 mpg over the S350, with little to no sacrifice in performance and luxury. Carbon emissions are also down by 21 percent. Mercedes said the gains are enough to make the S400 the most efficient car in its class. It should hit U.S. streets in September 2009.

Mercedes-Benz S-Class models have always been recognized for their smattering of the latest safety equipment, and the latest ones do not disappoint. One of its innovations is the PRE-SAFE Brake which can activate the maximum braking pressure if the driver fails to recognize the immediate danger of a rear-end collision. A feature called ATTENTION ASSIST is able to alert the driver if he or she is getting drowsy and Lane Keeping Assist vibrates the steering wheel if the driver starts drifting. Mercedes engineers have even improved the Active Body Control (ABC) suspension to compensate for the effects of crosswinds.

Perhaps the most important change for 2010 Mercedes-Benz S-Class range is the addition of a new model: the S400 hybrid. The Mercedes S400 achieves an estimated 29 mpg combined fuel economy, unheard of in its class. It manages such efficiency through a modified 3.5-liter V-6 engine, magneto-electric motor, seven-speed automatic transmission, and a high-voltage lithium-ion battery. The use of the high-tech battery in a car is a world's first. The 2010 S400 is also equipped with other common hybrid components such as regenerative braking and a start - stop function.

For 2010, the Mercedes-Benz S-Class gains its first-ever hybrid powertrain, a clear indication that its maker is shifting from a strict diesel approach to efficiency and finally acknowledging the worth of hybrids as an essential step on the path to electric propulsion. What's more, the 2010 Mercedes S400 Hybrid is the world's first production hybrid automobile using lithium-ion batteries (the Tesla Roadster is powered solely by Li-ion batteries). Hybrid propulsion systems aren't anything new, of course, but they're still rare in the luxury class, where the Lexus LS600hL has been standing alone for the past two years.

Instead of promising performance similar to an S-class with a larger engine, Mercedes chose to introduce its hybrid model as a more environmentally conscious way of traveling in luxury. The S400 Hybrid should cost about the same as the $90,225 V-8-powered S550 when it goes on sale in the United States this September. It uses the European-market S350 as a starting point, so behind the three-pointed star lurks a six-cylinder engine. The 3.5-liter V-6 produces 275 hp, the same as the base V-8 did in 2006, the last time a Mercedes-Benz S-Class was available to U.S. customers with a six-cylinder. And that V-8 didn't benefit from an additional electric motor.