Without a doubt, hybrid technology has made great inroads in reducing fuel consumption.  But so far, the most successful hybrids have been smaller cars and utilities.  It seems that as vehicles grow larger, the hybrid advantage gets smaller.  But that isn’t stopping Mercedes-Benz from making their biggest car, the S-Class, as responsible as possible. We applaud their efforts. But, will we like driving the results? 

The 2010 Mercedes-Benz S400 Hybrid is a new way for the socially elite to feel socially responsible. So, this big, elegant, gasoline-electric sedan targets efficiency by uniting a 275-horsepower 3.5-liter Atkinson-cycle V6 with a 20-horsepower electric motor and seven-speed automatic transmission to create a very competent and seamless mild-hybrid system. 

The S-Class is also the world’s first mass-produced vehicle with a lithium-ion battery.  The 120-volt battery is small and light enough to even reside inside the engine compartment. In fact, the entire hybrid system is so light and well-conceived, that it adds only 120 pounds to the standard S-Class. And of course, the system also has regenerative braking, as well an automatic stop-start function, which here cuts off the engine when braking below nine miles per hour.

So, what does all this hardware mean?  S400 Government Fuel Economy Ratings of 19 city/26 highway are, overall, about 17% percent better than the gas-only S550. And, the highway rating is better than its more established rival, the Lexus LS 600h L, a full hybrid sedan. Using premium gas, our mixed driving loop returned 20.2. That’s one mpg better than the last S550 we tested, but we did expect even better than that.

The S400’s Energy Impact Score is a moderate 16.3 barrels of oil consumed per year, with a similar Carbon Footprint of 8.7 annual tons of CO2. So, this sedan is not an eco-dream by any means, but it is the greenest option among full-size luxury cars to date.

With the electric assist adding 118 pound-feet of starting torque, full-throttle acceleration is better than you’d guess: 0 to 60 in a respectable 7.3 seconds, with a quarter mile in 15.7 seconds at 93 miles per hour. The S400 is not in any real hurry off the line, as the power build takes its time.  On the plus side, the engine is extremely smooth and quiet.  Gears are widely spaced, and using the steering wheel-mounted paddles makes for quicker shifts.

Suspension geometry is standard S-Class—multi-links front and rear. The Airmatic Air Suspension with adaptive damping links up with traction and stability control to produce an amazingly agile 4,500-pound sedan.

The S400 reacts more mid- than full-size. It's very stable and turn-ins are fairly quick. And, no matter how hard we pushed it, this big hybrid remained confident and balanced. Stopping power comes from four-wheel discs with ABS and Brake Assist. Even with a vague pedal, near fade-free stops from 60 averaged 128 feet. That's fine for such a massive beast.

On the outside, the S400 enjoys the latest S-Class facelift. Up front is a revised grille flanked by our car's active bi-xenon headlights. The profile wears larger side mirrors, and the rear integrates the exhaust outlets within a recontoured bumper fascia. The S400 identifies itself as a hybrid with a simple "Blue Efficiency" badge. Our tester also showed off 19-inch five-spoke AMG wheels as part of the optional Sport Package.

Inside, this airy S-Class cabin has all the latest upscale amenities and luxury features one could imagine, the most innovative being the split-screen interface shared between the driver and front passenger. It allows the passenger to watch a movie without distracting the driver.

Leather trimmed seats are deeply padded and supportive, and our car's optional wood/premium leather steering wheel had available heat.

Benz's voice-activated COMAND system, Tele Aid emergency communications, and 15-speaker Harmon/Kardon audio are standard. State-of-the-art safety advances like automatic braking, Distronic Plus adaptive cruise with lane departure warning, and Nightview Plus Pedestrian Detection, are options.

The always roomy three-person second-row adds eight-way power, and four-zone climate control with seat heat and ventilation as part of the Rear Seat Package. As for cargo, the trunk of the big S-Class measures a fitting 19.8 cubic feet, with under floor storage.

No S-Class is inexpensive, but the S400's base price is still genius. At $88,825, it's the least pricey S-Class. That's some 20 grand less than a Lexus LS Hybrid. Plus, the Mercedes qualifies for a tax credit of up to $1,150.

Still, it would be easy to dismiss the S400 Hybrid as a publicity stunt. But rather, we see it as another leg of Mercedes' fuel saving development program that also includes clean diesels, pure electrics, and hydrogen power. They want to make sure they posses the best technology for every vehicle class. And, yes, we did like driving the 2010 Mercedes-Benz S400 Hybrid, a smart move from an energy smart car company.


  • Engine: 3.5-Liter Atkinson-cycle V6
  • Horsepower: 275
  • Torque: 118 Lb Feet
  • 0-60 MPH: 7.3 Seconds
  • 1/4 Mile: 15.7 Seconds @ 93 MPH
  • 60-0 MPH: 128 Feet
  • EPA: 19 MPG City/ 26 MPG Highway
  • Mixed Loop: 20.2 MPG
  • Energy Impact: 16.3 Barrels Oil/Yr
  • CO2 Emissions: 8.7 Tons/Yr