Mercedes-Benz S400 Hybrid Review

By Jonathan Spira on 14 May 2010
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Mercedes-Benz introduced the world’s first diesel-powered automobile in 1936 and the company has been offering its customers fuel-efficient vehicles ever since. The S-Class, Mercedes’ flagship sedan, has been around since 1972 and got its name from Sonderklasse, essentially “a class of its own.”

For 2010, Mercedes designers gave their Übersedan a facelift.  From all outward appearances, little was changed.   The front of the car received a new grille and front bumper while the rear got an integrated exhaust.  LEDs are now used for taillights and daytime running lights.  But these minor exterior changes mask the significant updates found within.

The S-Class now has many of the new technologies introduced with the redesigned 2010 E-class, including adaptive high-beams, pedestrian detection in the night vision system, a lane-departure warning system, and the new Attention Assist driver drowsiness warning system.

Mercedes’ Autobahn cruiser continues to be one of the most comfortable, refined, and luxurious vehicles on the market.  It’s also now one of the most green, with the addition of the S400 Hybrid to the line-up.

The Mercedes-Benz S400 Hybrid has the distinction of several firsts.  It is the first production hybrid automobile to use lithium-ion batteries.  It’s the first Mercedes-Benz with a hybrid drive.  And it is also the first German flagship sedan to be available as a hybrid-electric (BMW has since introduced the Hybrid 7; Audi displayed a hybrid A8 concept car at the 2010 Geneva Motor Show. The first hybrid in the Über luxury sedan market is  the Lexus LS600h L but more on that later.).

The Mercedes-Benz approach to hybrids is one that adds less weight and complexity to the vehicle.  The mild-hybrid platform was jointly developed by BMW and Mercedes as an outgrowth of a cooperation that began in 2005.

A mild hybrid is a gasoline-fueled vehicle equipped with an electric motor that allows the engine to be automatically shut off whenever the car is braking, coasting, or stopped.  Mild hybrids differ from full hybrids in that they do not have an electric-only means of propulsion.  As a result, they do not require the same level of battery power and also do not achieve the same increase in fuel economy as full hybrids.

The S400 starts off with an Atkinson cycle 3.5-liter V-6 to which Mercedes added a 20-hp electric motor.  The motor serves merely to boost the engine power as it can’t propel the vehicle by itself; it adds 118 pound-feet of torque, something the car desperately needs as it takes 7.2 seconds to go from 0-60 (the gasoline powered S550 requires a mere 5.4 seconds).  The S400 is a big car and it does feel a bit sluggish.

The S400 displays its battery status from a display in the speedometer, which shows the flow of power from engine to battery to wheels.    When the car is stopped at a light or in traffic, the engine shuts down, thereby saving gas.  Simply taking your foot off the brake pedal causes the engine to restart.

Unlike its more powerful siblings in the S-Class lineup, the S400 Hybrid escapes the gas guzzler tax and gets 5 mpg more in the EPA’s city and highway ratings.  It also escapes the hybrid price penalty, perhaps most evident with the Lexus LS 600h L hybrid, which costs $40,000 more than its conventionally-powered stablemate, the LS 600, and gets only marginally-improved fuel economy.

On the road, the S400 Hybrid has the presence and feel typical of large Mercedes-Benz sedans.  One problem is the electric power steering assist, which allows the engine to stay off when the stop-start system turns it off, results in a driving experience that is largely devoid of any sensation (the S550, which foregoes electric steering, does not have this problem).

In a week’s worth of driving ranging from highway cruising to rush-hour traffic, I frequently found myself using 7.84 l/100 km (30 mpg).  Overall, I used 9.4 l/100 km (25 mpg), which was quite respectable  for the week.

I found the suspension (adjustable from sport to comfort) pampering and the air suspension kept the car well composed in the turns.  The most remarkable thing I found was just how unobtrusively the hybrid system behaved.  I hardly noticed the start-stop function (unless I was looking for it) and the car always restarted without a shudder.  The regenerative brakes, usually the weak point of hybrid systems, felt downright normal.

Finally, the fuel usage and emissions output of the S400 are simply laudable (the S400 is rated as a SULEV, or super low emissions vehicle).  In the coming years, German automakers, among others, will have to meet the ever-increasing fuel efficiency and emissions mandates set forth by European Union and U.S. regulators and the S400 Hybrid is one way to approach this.

The S400 compares favorably to Mercedes-Benz diesel offerings as well.  The S350 diesel is rated at 7.71 l/100 km (30.5 mpg) in fuel economy while the same test rates the S400 Hybrid at 8.11 l/100 km (29 mpg).

Although it’s unlikely that hybrid fans will allow the S400 to knock the Toyota Prius off its throne, the entry-level price point makes it likely that the S400 will become the best-selling S-Class and buyers will be able to enjoy the sumptuous Mercedes-Benz amenities knowing they are using less fuel with each trip.

2010 Mercedes-Benz S400 Hybrid
Base price/price-as-tested $87,950/$100,925
Drivetrain Front engine, rear-wheel drive
Engine 3.5 liter/275 hp/ V-6 with 20 hp electric motor
Transmission 7-speed automatic
Curb weight (lbs) 4594
Wheelbase (inches) 124.6
Length x width x height (inches) 206.5 x 73.7 x 58.0
0-60 mph (seconds) 7.2
City/highway fuel economy (mpg) 19/26