We've done a 180 in recent years. It wasn't too long ago that enthusiasm about fuel efficiency was the denizen of the lunatic fringe consumer, the dork putting wheel spats on the rear of a tiny car that resembles a root vegetable.
Today, we acknowledge that the geeks were on to something and a collective sense of responsibility is more pervasive. But, you know, we've still gotta be cosseted.
Enter the socially conscious luxury sedan. The 2012 Infiniti M35h and 2011 Mercedes-Benz E350 Bluetec reveal how much attitudes toward fuel efficiency have changed.
Of course, there's not a consensus on how to best crack the nut of a luxury sedan that sips less fuel. The German ekes out its efficiency gains through compression ignition, whereas the Japanese upstart takes the hybrid route. But it turns out that each one's respective choice of powertrain just scratches the surface. These luxury sedans have very different characters despite their similarities in size, mission and sticker prices.
The Diesel Mercedes and a Performance Hybrid
Ah, the diesel Mercedes. It's an institution that's been with us since the days of Methuselah and has managed to be at once offbeat yet omnipresent, timeless rather than trendy. The professorial diesel Mercedes is the argyle socks of the automobile world.
Today's diesel Mercedes, the E350 Bluetec, brings a 3.0-liter turbodiesel V6 that generates 210 horsepower at 3,400 rpm and fully 400 pound-feet of torque from 1,600-2,400 rpm. All that twist drives the rear wheels through a seven-speed automatic transmission. Its exhaust is scrubbed squeaky-clean with a urea-based after-treatment system, and its window sticker reads 22/33 city/highway mpg. It'll set you back $63,120 when equipped like our tester, which is pumped up with $12,000 in options.
This toes up nicely to our Infiniti M35h tester's $65,395 price tag, of which $10,800 is bits, baubles and destination. The M35h marries a gasoline-fed 3.5-liter V6 to a hybridized seven-speed transmission, which is in turn fed electrons by a lithium-ion battery pack that's mounted in the trunk. Combined output peaks at a heady 360 hp and its EPA numbers are 27/32 city/highway mpg.
At 4,163 pounds, the M35h is 126 pounds heavier than our V8-powered M56 long-termer, owing to the placement of its batteries aft of the rear seat. Thus it's easy to assume that the resulting rearward shift of the M35h's weight distribution would be a good thing for handling, and in routine driving there's little to dispute this. The M35h is more alert in this pursuit than the E350.
Flung in anger, the M35h's extra weight becomes more evident, lending it a sense of ponderousness. Its steering suffers slightly in the conversion to all-electric, requiring constant subtle corrections around center on arrow-straight freeways. Still, as electric steering goes, the M35h's is well-executed.
Neither of these cars would be your first choice for tackling your favorite back roads. They're not cut from sport sedan cloth. But among the pair here, the E350 — while certainly no Boxster — complies more willingly than the more nervous M35h. The E350's steering is too slow and a shade mute, but its linearity instills confidence. Ride quality, too, goes to the E350 Bluetec, which simply dispatches irregularities better than the more fidgety Infiniti.
Indeed, the stolid, staid diesel Mercedes boasts the more accomplished chassis of the pair. It's about breadth of capability — the Benz is consistently planted and secure regardless of speed. Though their handling numbers are similar — the Merc's 0.82g skid pad and 63.9-mph slalom performances are just 0.01g and 0.8 mph higher than the M35h — the Benz drives more naturally.
One pleasant surprise is the M35h's braking characteristics in routine driving — unlike in most hybrids, you can actually modulate the brakes without looking as if you just got your learner's permit. Drop the anchors hard and they lose some composure, though they haul the big sedan from 60 mph to a halt in a reasonable 122 feet. The Mercedes' stoppers did the same task in 116 feet, and have a solid, linear pedal.
Eat My Hybrid Dust
When the road straightens, as it inevitably does, the Benz gets absolutely manhandled by the M35h. Squeeze the "gas" in the Infiniti and you're punted down the road on an electrically assisted wave of thrust. The M35h's big, beefy wad of torque might reshape your perceptions of what a hybrid can do.
And just what can it do? At the test track, the M35h hit 60 in 5.5 seconds (5.1 seconds with 1 foot of rollout like on a drag strip) and ran the quarter-mile in 13.8 seconds at 100.8 mph. The Mercedes, meanwhile, was somewhere far behind, making its way to 60 mph in 7.7 seconds (7.3 seconds with rollout) and clicking the quarter at 15.5 seconds at 89 mph.
There's more. The M35h's first acceleration run trapped faster still at 102.5 mph, a consequence of its sensitivity to its battery's state of charge. This variability in performance is endemic to all hybrids, but despite this, an M35h at its slowest is much quicker than an E350 Bluetec at its fleetest. It's not even close, and if you place a priority on a hasty departure, there's only one car to consider in this pair.
That's not to say the E350 Bluetec is a slug. In fact, its straight-line urge rarely feels lacking, as even just off idle the diesel mill generates ample boost. The E350 Bluetec packs a solid midrange, too. Inevitably, the Bluetec peters out just before the tach reaches its (low) redline, though the flexible automatic keeps the diesel in the meat of its power production and swaps gears reasonably quickly.
The E350 Bluetec may not blur the scenery the way the M35h does, but the diesel has manners on its side — the Bluetec is more seamless in around-town use than the M35h's hybrid powertrain, which awakens its gasoline V6 with a noticeable lurch.
Many drivers wouldn't even know this was a diesel from the driver seat. Telltale diesel clatter has been banished from the cabin of the E350. Only if you step outside the vehicle does the diesel audibly tip its hand.
The Great Divide
After spending several hundred miles driving each car, the philosophical gulf between their makers becomes evident in the details. Take the doors, for example. The Infiniti's door handle is feather light, and its door whips open as if it was filled with helium. Operating the E350's door and handle is a more distinctly mechanical experience, with a fluid heft that's not unlike swinging open a vault.
Other controls in the M35h fall in line — the steering wheel, brake pedal and throttle all operate slickly and with almost no effort. Luxury according to the Infiniti is to not disturb the owner: to minimize its operator's workload and to fade into the background.
The Mercedes suggests that solidity is the desired virtue. There's a real sense of gravitas in its controls, the ride, even the power delivery. This diesel engine's robust character dovetails nicely with the impression of unburstability you get when driving the current E-Class. It's not all an illusion, unfortunately, as our E350 tester weighs fully 4,242 pounds.
Despite its similar mass, the M35h doesn't quite convey the same impression. Its isolation from road noise is not as comprehensive as the E350, and the driving experience can't match the E350's rocksteady-ness. Then again, few cars can.
The Ups and Downs of Hauling Batteries
Both of these sedans are equipped with more modern conveniences than a Fry's electronics store. For instance, the Bluetec boasts a massaging driver seat, an infrared imaging system and headlights so capable they're practically self-aware; our M35 tester's blind spot alerts, adaptive cruise, collision alert and lane departure warning systems are, apparently, straight out of NORAD. And both of their cabins offer sumptuous comfort and space.
Instead, the differences lurk in the kind of basic conveniences we take for granted these days. Take trunk space. The lithium-ion batteries of the M35h's hybrid system gobble up volume, leaving 11.3 cubic feet remaining for your bags. Plus the Infiniti's backseats are necessarily fixed in place. The E350's 15.9-cubic-feet cargo area is comparably vast. Go ahead, put the golf bags and the caddies in the Merc's trunk. A 60/40-split folding job is, oddly enough, a $440 option with which our E350 tester was not equipped. Go figure.
As-tested fuel economy for both sedans was identical at 24.4 mpg, but there's a caveat. These cars' colossal range meant few data points. Though subjected to a broad spectrum of driving from city to freeway cruise and everything in between, it simply wasn't possible to put multiple tanks of fuel through them during our allotted time. Call our results provisional and indicatory. Still, the M35h's straight-line thrust is tempting, and we were glad to oblige, over and over again. Yet despite this, its fuel consumption was no worse than that of the Bluetec. If you're thinking cake-and-have-it, you're not alone.
Hybrid Takes the Brass Ring
Here, then, we have two very different luxury sedans that are influenced by their powertrain choices rather than defined by them. With its traditional values and robust character, the E350 Bluetec has a refreshing honesty. It is unquestionably among the world's best long-distance cruisers. There's a lot to like here.
Our CAFE-focused new world order will bring ever stronger and cleverer diesels and hybrids. Today, though, the M35h's electrically enhanced potency is irresistible, and ultimately helps the Infiniti edge out the Merc for the win. Moreover, its effortless thrust doesn't come at the expense of consumption, and its hybrid nature doesn't spoil the plot. The Infiniti M35h hones the performance hybrid concept to its sharpest edge yet.
It might even turn us into spat-wielding dorks.
The manufacturers provided Edmunds these vehicles for the purposes of evaluation.