Th lithium-ion battery pack was – and is – controversial. Under some circumstances, this variety of battery has been known to overheat and occasionally burst into flame. So far, so good for this model, on that score.
A thin electric motor between the engine and transmission supplemented a 3.5-litre V6, and the entire drivetrain developed some 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 closest rival to the S400h, was thriftier in town but thirstier on the highway.
The 2010 S400h was a “mild” hybrid. It couldn’t propel itself on battery power alone and the electric motor acted as a starter as well as supplying more power when needed. It 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 and/or hit the brakes.
The 3.5-litre V6 unit was taken from the S350 and, among other things, it featured an Atkinson cycle valve arrangement, which basically 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 grade 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, Bluetooth connectivity, and on and on.
It also came with Mercedes’ Attention Assist system, which monitors the driver, taking note of their driving behaviour, evaluating it, and providing a warning at the onset of fatigue or drowsiness.
The Premium package included self-massaging front seats and a backup camera.
Virtually all functions for the S400h were accessed via a stationary mouse and rotary dial located on the centre console (very similar to that in some Lexus products). Some drivers found this counterintuitive and laborious. To pre-set a radio station, for example, took four steps. And the S400h warned the driver to not allow the system to divert their 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. The latter organization, however, did have 15 technical service bulletins for this year of the S class. For example, there were 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’ parking assist program.
Consumer Reports liked the S-class. Said CR: “the S-class has always been stately and luxurious,” and “the ride is still first class, but handling is fairly sporty as well.”
Marketing researcher J.D. Power rated the S-class highly when it came to things like powertrain mechanical quality, and body and interior quality design. But they were less enthusiastic about its powertrain design. It received a “better than most” rating for overall quality.
Comments from owners:
- “excellent phone and navigation system;”
- “really high quality seats;”
- “temperature control sometimes a little off.”
The S400h was not one of the company’s high-volume models and a used one can be hard to find. From a base price of around $110,000, it has dropped in value by at least half. Depending on equipment level, expect to pay anywhere from the low $40,000s to the low $50,000s.
2010 Mercedes S400h
Original base price: $105,900
Engine: 3.5 litre V6, electric motor with lithium-ion battery pack
Horsepower, torque: 295, 284
Transmission: seven-speed automatic
Fuel economy (litres/100 km): 11.0 city and 7.7 highway, with premium gas
Some alternatives: Lexus LS600h, BMW ActiveHybrid 7
Ted Laturnus writes for Troy Media’s Driver Seat Associate website. An automotive journalist since 1976, he has been named Canadian Automotive Journalist of the Year twice and is past-president of the Automotive Journalists Association of Canada (AJAC).