Great Ride, Difficult Brakes, Good Big-Car Fuel Economy, that’s what I wanna to say
With its 2010 S400 Hybrid, Mercedes-Benz has taken some significant steps to redefine the premium hybrid sedan market - in part by minimizing the premium.
Despite cutting-edge technology that includes what the automaker says is the world’s first lithium-ion battery designed specifically for automotive use, Mercedes-Benz new entry-level U.S. is priced staring at $88,825, nearly $4,000 less than the S550 that previously was the entry-level S-Class in the U.S.
Of course, being an S-Class model, the S400 Hybrid still offers a high level of luxury and a cavernous interior, along with the same refreshed body styling as the rest of the 2010 model line. Passengers and passersby would be hard-pressed to distinguish it if there weren’t Hybrid badges on the trunk lid and the center stack, and BlueEfficiency badges on the front quarter panels.
But the S400 Hybrid’s difference is unmistakable from the driver’s seat - where we logged hundreds of miles over two days last weekend, with decidedly mixed emotions.
Innovative Battery
The leading innovation in the S400 Hybrid is the aforementioned 120-volt, 0.9 kilowatt-hour lithium-ion battery that’s small enough to fit into the engine compartment - like an ordinary car battery - rather than beneath or behind the seats, as in other hybrid vehicles.
There’s no compromise in terms of people room or trunk space. And even with a high-strength steel housing, its own separate cooling circuit and cells that sit in a vibration- and jolt-dampening gel, the battery still weighs less than most others, and also has a higher energy density, according to Mercedes-Benz.
It’s a so-called mild hybrid because the system doesn’t propel the S400 on electricity alone, but there’s still plenty of power and a decent fuel economy bump other gasoline-fueled S-Class models, including the the European market S350 on which it is based.
A 20-horsepower magneto-electric motor mounted in the torque converter housing between the engine and the transmission produces 118 pound-feet of torque, and kicks in during acceleration, to assist the 275 horsepower, 3.5-liter V6 gasoline engine (which generates 258 lb.-ft. of torque) in driving the rear wheels. The usual stop-start scheme turns the engine off when the car isn’t moving.
The result is a fuel economy rating of 19 miles per gallon in the city and 26 mpg on the highway, a 30 percent improvement over the S550’s mileage rating.
Compared with the V6-powered S350 sold in Europe, Mercedes-Benz says the S400 Hybrid also produces 21 percent less CO2 emissions.
Acceleration is respectable but not awe-inspiring: 0-60 mph in 7.2 seconds, Mercedes-Benz says.
Edmunds Inside Line published a thorough first drive review of the car’s prototype last year, explaining its technology innovations and driving demeanor in great detail - and it remains relevant: The S400 Hybrid you can now buy is much the same.
The first time I slipped behind the wheel in the S400 Hybrid was actually a week before our weekend excursions, on a 20-minute joyride at Test Days, an annual confab for auto writers held in Pennsylvania’s Pocono Mountains region.
It was a brief fling, but long enough to form a first impression that was reinforced during my recent weekend with the car: While the ride, in classic S-Class style, was exceptionally pleasant and refined, the performance of the hybrid-specific regenerative braking system left me feeling insecure. And real-world fuel economy, although very good for such a large and heavy (4,474 pounds) car, was not stellar.
Fuel Economy May Vary
Beginning with a full tank of gas on Saturday morning, I drove the car in a mix of suburban and highway-speed driving in and between Hoboken and Ridgewood - (two ‘Jersey towns in the New York City metro area), at speeds ranging up to 60 mph.
Gas mileage on the drive peaked at about 30 mpg, according to the car’s trip computer. Following the return trip from Ridgewood - having reset the display before we started the 26-mile one-way leg - the car reported average fuel economy of 21.3 mpg.
On Sunday, after resetting the trip computer again, we drove from Hoboken, NJ to Milford, Pa., and Raymondskill Falls in the nearby Delaware Water Gap National Recreation Area, with a stop en route at Lafayette, NJ, then back to Hoboken via the Dingmans Bridge, with a stop in Roseland, NJ.
After the first leg to Lafayette, we logged 56 miles at an average speed of 48 mph, with average fuel economy of 27 mpg, and the gas gauge had barely budged. Twenty miles later, having slowed down for rural driving, we reached our destination - Grey Towers National Historic Site in Milford. The car now reported our slower average speed of 41 mph, and an average fuel efficiency for 76 miles of 25.6 mpg. The gas gauge showed three-fourths of a tank remaining.
We next put 10 more miles on the trip computer, driving in Milford and then on to Raymondskill Falls, lowering our average speed to 34 mph and our average fuel economy after 86 miles to 23.9 mpg.
Once again, before our return, we reset the trip computer. Traveling 54 miles to Roseland, we logged an average speed of 40 mph and average mileage of 27.4 mpg. The gas gauge barely dropped.
By the time we reached Hoboken and found a parking spot , the trip computer said we had gone 78 miles since Raymondskill Falls at an average speed of 32 mph and average fuel economy of 25.3 mpg. The gas gauge showed five-eighths of the tank remaining.
Monday morning, after another trip computer reset, we drove one more mile around Hoboken to look for a new parking spot. Our average speed was just 3 mph, and we logged average mileage of only 12.3 mpg.
Overall, after 217 miles of mixed city and highway travel, average fuel economy cam in at just about 24 mpg, slightly higher than the EPA combined figure of 22 mph.
Brakes with a Learning Curve
All that driving reinforced our belief that Mercedes-Benz’s “Drive-Dynamic multi-contour front seats with 4-stage massage function” (part of a $4,950 options package) are among the best car seats we’ve ever experienced. The “slow and vigorous” massage relaxed us greatly.
Yet even these excellent seats didn’t help us overcome our anxiety about the S400 Hybrid’s “three stage” braking.
Mercedes-Benz explains it this way: When the car is coasting, the magneto-electric motor, already acting as a generator, recovers energy and helps to slow the car down. Lightly touching the brake pedal increases the motor’s output as a generator, slowing the car further. But it’s only by pressing hard on the brake pedal that the driver can initiate the third braking stage, in which the car’s actual wheel brakes are engaged. “These three stages are controlled seamlessly, so the driver perceives the new system simply as smooth, responsive braking,” the company says.
That wasn’t how it worked, however.
On more than one occasion, what felt like normal pressure applied to the brake pedal didn’t slow the car quite fast enough. To avoid overshooting turns at intersections, I ended up applying what seemed like emergency braking pressure. To make sure the S400 Hybrid didn’t plow into other cars from behind when they were braking, I was careful to maintain extra-long gaps to the car ahead. Parallel parking, when most drivers tend to feather the brake pedal, was equally treacherous.
Braking smoothly required great effort - mental as well as physical.
If ever a Mercedes-Benz were in need of the optional Driver Assistance package ($2,900), which includes the automaker’s very effective DISTRONIC PLUS adaptive cruise control and PRE-SAFE Brake automatic emergency braking systems, the S400 Hybrid is it.
The Road Ahead
Overall, the S400 Hybrid is a superlative luxury sedan in the S-Class tradition, offering better fuel economy than its brethren as well as green car bragging rights. But we might prefer the back seat to the driver’s seat - and leaving the job of driving it smoothly to a professional chauffeur.
If, however, you prefer an S-Class with more get-up-and-go, and want even greater green-car street credibility, just wait.
At the recent Frankfurt Auto Show, Mercedes-Benz previewed the Vision S500 Plug-In Hybrid concept.
It uses a lithium-ion battery with slightly more than 10 kilowatt-hour of storage capacity, a 60-horsepower hybrid module and a V6 gasoline engine with direct injection.
With 0-60 mph acceleration pegged at a brisk 5.5 seconds, its driving range in electric-only mode is said to be 18 miles, while claimed fuel economy is about 73 mpg.
