Rating: 9.4
Bottom Line:
Fully capable but without the pretense of more visible brands in the mid-size luxury field, the Infiniti M-series enjoys a faithful following. The all-new third-generation "M"s promise to build on that foundation.
Pros:
  • Much improved V-8 power
  • Strong styling; impressive detailing
  • Every bell and whistle, each one adjustable
Cons:
  • Minor loss in headroom
  • Sport model seats could be snugger
  • Standard sunroof is small

View Pictures:  Infiniti M

Trendy midsize luxury performance sedans don't have the option of growing old in their demanding market; there's simply too much competition. That is why Infiniti is releasing an all-new series of M sedans. On sale in March 2010, the 2011 M37 and M56 pack more power, better fuel economy and a new 7-speed transmission in a chassis more rigid than ever before. Toss in a host of new electronic bells and whistles and statement-making styling changes, and you get an elegant yet sporty package that is designed to satisfy.

Model Lineup
Strictly a 4-door sedan, the Infiniti M series lists four 2011 versions: the rear-wheel-drive 6-cylinder M37; the all-wheel-drive 6-cylinder M37x; the rear-wheel-drive V8 M56; and the all-wheel-drive V8 M56x.

In addition, there are the M37 Sport and the M56 Sport. Both Sport iterations are badged as such and are significantly different in both trim and function to seem like separate models. The Sport Package is not available with AWD.

Infiniti says customers asked for more differentiation in the Sport Package, so besides the firmer suspension tuning, active rear steering, larger 14-inch brakes and larger performance tires, it now includes a different fascia, darker grille and headlight trim. Inside, the seats are more heavily bolstered, the steering-wheel rim is meatier and both get matching leather trim. Aluminum accents set off the sport pedals, too.

All M's ride on 245/50R-18 all-season radials mounted on 18-inch 5-spoke cast aluminum wheels. Optional are the 245/40R-20 summer tires on split-spoke 20-inch aluminum wheels from the Sport Package.

Under the Hood
Both the standard V6 and optional V8 engines were re-engineered for 2011. Gaining 27 horsepower, the upsized 3.7-liter V6 makes 330 horses and 270 lb-ft of torque. A real revver with a 7500 rpm redline, the V6 makes best use of the new 7-speed automatic transmission. It can be manually shifted, either with the standard center console shifter on base cars or via steering-wheel-mounted paddle shifters with the Sport Package. Left in auto, the transmission rev-matches on downshifts, so gear changes will seem smoother.

But the big news here is the M56's all-aluminum, double overhead cam, 32-valve V8. Now a massive 5.6 liters, it features direct fuel injection and develops 420 horsepower (that's a game-changing 95-horse gain from last year) and a muscular 417 lb-ft of torque.

Fuel economy has risen only 1 mpg to 18 mpg city/26 mpg highway with the rear-wheel-drive V6. But the V8 overachieves at 16/25. That's a gain of 4 mpg on the open road thanks to the new transmission. Both engines require premium gasoline.

Other improvements are a revised independent rear suspension for reduced weight and better handling. The Sport Package's rear steering is computer controlled, signaling a small electric motor to steer the rear wheels out of phase with the front wheels for easier parking, and in phase at speeds above 25 mph for greater stability.

Maximizing the power of electronic engine and transmission controls is an M sedan exclusive Drive Mode Selector, which varies throttle progression and transmission shift mapping to suit your driving style. This rotary knob on the center console selects one of four modes: Standard, Snow, Sport and Eco. And, surprisingly, it does make a noticeable difference in the M's response. We thought it a gimmick at first, but came to enjoy rapidly retuning the car. Not as immediately apparent but definitely useful is a full suite of electronic braking, stability, blind-spot intervention and cruise-control distance and lane discipline aids.

Inner Space
Wood and leather set the tone in the inviting M cabin, a luxurious environment in an active, participatory way. The M follows through on the inviting, flowing design with generous front and good rear-seat room. Just a touch of rear headroom was shaved when redesigning the roof, but few will notice.

The standard trim is elegant, with genuine Japanese ash wood accents and quality leather trim. Both the Sport and Touring packages retrim the interior; the former more athletically, the latter more sumptuously. The seats change noticeably between the trims. The standard and Sport seats give typical upscale sedan support; we'd enjoy tighter bolstering on the Sport, but as is, it's broadly accommodating for long hauls. Like a pillow-top mattress, the heated and cooled Touring seats are ultraplush on top with firm support below.

In fact, the Deluxe Touring Package goes all-out for the country club ambience, with semi-aniline leather, a suedelike headliner, white ash wood trim and a power rear sunshade.

Infiniti says it's making a genuine effort at a luxury interior, using Infiniti-specific switches, for example, rather than relabeling parent company Nissan's gear. The color palette, materials and design are sophisticated, so the effort delivers.

Electronically, the M's keep pace with all the latest active noise canceling, navigation, restaurant guide concierge and optional 14-channel, 16-speaker sound systems with 9.3 gigabytes of storage for digital music. Infiniti scores well for intuitive, highly functional controls, but is reaching with Forest Air, its trademark for filtered, humidity-controlled air conditioning that alternately blows from upper and lower vents to better mimic natural airflow.

On the Road
The M sedans deliver that rare combination of luxury and driving fun. The performance is stimulating, the luxury built-in and the numerous details well-executed.

In a way the M37 and M56 are two different cars, with the Sport and Touring packages making it more like four. The V6 does not lack for power, asking only to be revved when extra thrust is needed. Inherently lighter and better handling, the M37 snarls when provoked, and the Sport Package's paddle shifters fit the car's character.

Not feeling much weightier but socking with a prizefighter's punch, the M56 gets — but doesn't need — paddle shifters. Nor does it really need half of the transmission gears, for that matter. It simply rolls out speed in massive swells of quiet power.

In Touring mode each car leans distinctly to relaxed comfort. As a Sport everything tightens up. We found the Touring versions felt a bit floaty when driven enthusiastically on back roads, while the Sport gave away little in comfort for large increases in surefootedness and enthusiasm. Matched to the powertrains, the M37 Sport is a natural, while the M56 does the Touring package best.

The powertrain tuning is refined, but it shows a bit of lash or hesitation when asked to emulate a sports car with snappy on-off inputs. Twisting the Drive Mode Selector gives instant results. In Eco mode, gas mileage improves for the average driver, but responsiveness is oatmeal soggy. Sport mode is clearly sharper all around — throttle response and shifting — while Standard falls in between.

Right for You?
Pricing is relatively unchanged, considering the large increases in content and performance. The M37 is up about $450 to a base price of $46,250, or $48,400 for the AWD M37x. The M56 gained $2,000 on the sticker to $57,550, but the M56x is just $750 more expensive, at $60,050, because it no longer pays a gas-guzzler tax.

Leasing is popular in this segment, and this option is within pocket change in price.

Functionally the M series fulfills all needs; it's a sweet-driving, powerful luxury sedan. Probably its biggest drawback is in perceived status, something only a blue-and-white or three-pointed-star logo seems to cure. For those secure in their status, the M is definitely worth a look.

Longtime Road & Track contributor Tom Wilson's credits include local racing championships, three technical engine books and hundreds of freelance articles.