Based on the S350 platform, Mercedes' S400h hybrid was introduced in 2010 and was the first Mercedes sedan to receive a hybrid drivetrain and the first to utilize a lithium-ion battery pack.
This latter item was – and is – controversial. Under some circumstances, this variety of battery has been known to overheat and occasionally burst into flame. No such reports for this model, however.
A thin electric motor located between the engine and transmission supplemented a 3.5-litre V-6, and the entire drivetrain developed 295 horsepower at 6,000 rpm. Combined fuel economy was in the 8.0 litres/100 km neighbourhood, which was superior to the S350 it was based on. The Lexus 600h, the S400h's closest rival, was thriftier in town, but thirstier on the highway.
The S400h was also a so-called "mild" hybrid. In other words, it couldn't propel itself on battery power alone, and the electric motor supplied more power when needed. The hybrid system also shut the powertrain off when the vehicle came to a stop and restarted itself when you took your foot off the brake pedal – pretty standard fare these days. Like virtually all hybrids, the S400h had a regenerative braking system that recharged the batteries when you decelerated or hit the brakes.
The gasoline engine was a 3.5-litre V-6 unit taken from the S350, and suitably modified. Among other things, it featured an Atkinson cycle valve arrangement, which means that the intake valves stay open a smidgeon longer to take maximum advantage of the combustion process. While this is good for fuel economy, it takes away from performance. Transmission was Mercedes' ubiquitous seven-speed, and the S400h required premium gasoline. A road-burner it was not.
Being a Mercedes, it came with a full roster of features designed to pamper its occupants. Standard equipment included full leather interior, heated steering wheel, heated/ventilated front buckets, electronic parking brake, power rear window sunshade, intelligent cruise control, steering wheel shift paddles and Bluetooth connectivity.
It also came with Mercedes' Attention Assist system, which monitors the driver, taking note of his/her driving behaviour, evaluating it, and providing a warning at the onset of fatigue or drowsiness. The optional Premium package included self-massaging front seats and a back-up camera.
Virtually all functions for the S400h were accessed via a stationary mouse and rotary dial located on the centre console (similar to that found in some Lexus products). Some drivers found this setup to be counter-intuitive and laborious. To pre-set a radio station, for example, took four separate steps, and the S400h displayed a warning to the driver to not allow the system to divert his/her attention from traffic and road conditions as soon as they turned on the ignition.
No safety recalls for this one either from Transport Canada or the U.S. National Highway Traffic Safety Administration. NHTSA, however, does have 15 technical service bulletins for this year of the S class. For example, there are engine cooling issues with virtually all variations of this model, a complaint about a "cracking" noise when the height adjustment is activated on the front seats, steering wheel "vibrations" and a complaint about Mercedes' Parktronic parking assist program.
Consumer Reports doesn't have much to say about the S400h, but does like the S-class in general. Says C.R.: "The S-class has always been stately and luxurious" and "the ride is still first-class, but handling is fairly sporty as well."
Market research firm J.D. Power, meanwhile, rates the S-class highly when it comes to powertrain mechanical quality and body and interior quality design, but is less enthusiastic about its powertrain design. It gets a "better than most" rating for overall quality. Comments from owners: "Excellent phone and navigation system," "Really high-quality seats" and "Temperature control sometimes a little off."
The S400h was not one of the company's high-volume models. From a base price of less than $110,000 in 2010, it has dropped in value by at least half. Depending upon equipment level, prices for this luxury hybrid start in the low-$50,000 neighbourhood, going up to the mid-$50,000s.
2010 Mercedes-Benz S400h
Original Base Price: $105,900; Black Book: $54,250; Red Book: $51,425
Engine: 3.5-litre V-6/electric motor with lithium-ion battery pack
Horsepower/Torque: 295 hp/284 lb-ft
Transmission: Eight-speed automatic
Fuel Economy (litres/100 km): 11.0 city/7.7 highway; premium gas
Alternatives: Lexus LS600h, BMW ActiveHybrid7
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