Review

The 2011 Infiniti M37 is the V6 version while the 2011 Infiniti M56 features the V8.

Both are available with all-wheel-drive, denoted by M37X and M56X. The M37X and M56X feature a part-time computer-controlled drive system to add engine power to the front tires when the driving situation calls for more traction. Sports suspensions are available for the rear-wheel-drive M37 and M56 models, and a hybrid version is scheduled to join the lineup.

The Infiniti M competes in the entry luxury sedan market segment with the Acura RL, Lexus GS, Audi A6, Mercedes-Benz E-Class, and BMW 5 Series.

Infiniti's V6 and V8 powertrains have received substantial upgrades for 2011, with far more torque and horsepower available from both engines. With a 330-horsepower V6 engine, the most powerful in its class, the M37 offers 27 additional horsepower, 18 more foot-pounds of torque, and far better acceleration performance than the outgoing M35. Similarly, the V8 engine, enlarged from 4.5 to 5.6 liters, fitted with direct fuel injection and variable valve timing and lift, produces 420 horsepower, or 95 horsepower more than the M45 of last year, and 417 foot-pounds of torque, or 81 more than the M45 engine.

Both engines now use a 7-speed automatic transmission with manual shift override, which yields better acceleration in the lower gears, and significantly better highway fuel mileage, up to four miles per gallon better, than the smaller, less powerful engines with the old 5-speed automatic transmission. The new transmission features four driving modes, including Normal, Sport, Economy and Snow, controlled by a knob on the center console. Sport models include magnesium paddle shifters with blip-throttle downshifting.

The width of the 2011 Infiniti M is increased by 1.5 inches over the previous version, to 72.6 inches wide. The overall height has been lowered by 0.3-inch (to 59.1 inches). However, the wheelbase is unchanged at 114.2 inches, and the length has grown by just 0.6-inch (to 194.7 inches). The front track increased by 1.5 inches on rear-wheel-drive models to 62.0 inches and the rear track has been increased 0.8 inches to 62.0 inches. (The track is the distance between the left and right wheels.) For AWD models, the front track has increased 0.9 inches to 62.0 inches and the rear track has increased 0.6 inches to 61.6 inches.

With all the changes, the new M is about the same weight as the old car because of lightweight material substitutions such as aluminum doors. The body shape and some underbody trickery yield a coefficient of drag for the new body of only 0.27 Cd, the world's lowest for a four-door luxury car.

Befitting and proper on any modern luxury sedan, the 2011 Infiniti M line bristles with electronic technology to make driving safer and more enjoyable. For instance, the M cars are available with a blind spot warning system that beeps to tell the driver there is a vehicle in the mirror's blind spot. The M also carries a lane departure warning system to warn the driver that he or she has crossed the centerline of the highway. If the driver doesn't respond to the warning, the blind spot intervention system steps in and applies the right front brake to gently guide the car back into the lane in which it belongs.

For audio enjoyment, there are three different sound systems on the M cars, including two Bose system upgrades. The Premium Package includes a two-channel, 10-speaker sound system by Bose, the Deluxe Touring Package adds a 5.1 surround sound system with a subwoofer and 16 speakers arrayed throughout the interior.

We found the Infiniti M56X has a lovely, sporty driving demeanor. The active noise-canceling system works very well, perhaps too well, because the cabin is so quiet that exterior factors like tire noise and wind noise around the mirrors can intrude. The cabin is gorgeous and roomy, although the rear seat headroom was reduced to obtain the new shape, and the controls arrayed around the 8-inch screen are very easy to use.

Line-Up
The 2011 Infiniti M lineup includes the V6-powered M37 ($46,250) and M37X all-wheel drive ($48,400), and the V8-powered M56 ($57,550) and M56X all-wheel drive ($60,050).

Standard features on all Infiniti M models includes leather seating and trim, eight-way power seats, dual-zone climate control, a multi-function steering wheel with cruise control, AM/FM/CD/MP3 sound system with AUX plug iPod compatibility, power windows, mirrors, and locks, and HomeLink garage door opener.

The Premium Package ($3,350), optional on M37 models, standard on M56 models, adds the Navigation system with 8-inch display screen, Bose two-channel, 10-speaker audio, 9.3 gigabyte Music Box hard drive, Bluetooth streaming audio, climate controlled front seats and a heated steering wheel.

A Deluxe Touring Package ($3,800) features higher-grade interior materials including semi-aniline leather seats and a faux suede headliner, special stitching and patterns on the upholstery and dash, an upgraded Bose digital 5.1 surround sound system with 16 speakers, four mounted on the tops of the front seats, power rear sunshade, and a special white ash wood trim hand-rubbed with silver powder. A unique feature of the Deluxe Touring package is the Forest Air system that not only filters and purifies incoming air, but also is programmed to blow gentle breezes into the cabin periodically, and control cabin humidity.

The Sport Package ($3,650), for rear-drive M37 and M56 only, adds active rear steering, sport suspension, sport seats, 20-inch performance tires and alloy wheels, larger brake discs and calipers. Sport models get dark chrome trim on the unique Sport grille, headlight surrounds, and alloy wheels. A Sport Touring Package ($2,000) adds the Bose 5.1 studio surround sound system, Forest Air and rear sunshade to Sport models.

The Technology Package ($3,000) adds Blind Spot Warning, Blind Spot Intervention, Active Trace Control (a form of yaw control), Intelligent Brake Assist, Forward Collision Warning, which will actively brake the car if audible warnings are ignored, and an Eco Pedal, which pushes back on the driver's right foot if driving is too aggressive for good fuel economy. Infiniti claims a 5-10 percent fuel economy improvement if the driver uses this pedal religiously.

Freestanding options include 18-inch alloy wheels and an aero package.

Safety features that come standard on all 2011 Infiniti M models include dual-stage front air bags with seat belt and occupant classification sensors, side-impact air bags, and roof-mounted curtain air bags for front and rear-seat outboard occupant head protection. Active safety features on all models include anti-lock brakes (ABS), and electronic stability control. The optional Technology Package further enhances safety. The all-wheel drive that comes on M37X and M56X models further improves handling stability in slippery conditions. Infiniti M models come with excellent seat belts with force limiters and pretensioners, so be sure to wear them.

Walk Around
The Infiniti M exterior design is all new for 2011. The design is reminiscent of Infiniti's Essence concept coupe introduced summer 2009, but with four doors instead of two. It is altogether more swoopy, curvaceous and modern than the previous middle-of-the-road M designs, with a pleasing combination of more curvature and less chrome. The body and underbody are aerodynamically pure, leading to a very low 0.27 drag coefficient, and that leads to a quieter interior, among other things.

Infiniti says the long-hood, short-deck design conveys that the M is a rear-drive sedan, with the severely laid-back windshield and the flowing fenders and body lines accentuating its sportier nature. They say that, for its size, it has the largest interior volume and largest trunk space in its class.

The M line carries high-intensity xenon headlamps, with adaptive lighting optional. A power tilting sunroof is standard, as are power folding and auto-reversing mirrors.

Interior
The 2011 Infiniti M has been completely redesigned inside. Everything in the cockpit has been redesigned to be more luxurious to see, touch and use, with beautiful design work on every piece and higher quality materials throughout. The steering wheel, wheel controls, instrument panel, center stack, center console, door panels and seats, all have been redesigned and upgraded.

The intelligent key system used on the 2011 Infiniti M incorporates the normal unlocking and locking features but adds audio setting, climate control settings and navigational settings to the memory in the key, an interesting and useful feature not offered on most luxury cars.

Every M car uses active noise control inside the cabin, a dual microphone system that listens to the ambient noise created by the powertrain, the mirrors, the body, and the tires and produces sound waves that cancel those noises. Even at triple-digit speeds and lots of throttle, the M is very quiet inside.

Driving Impressions
We found the 2011 Infiniti M56X, equipped with all-wheel drive, Deluxe touring package, and Technology Package, to be a very high performer. The added weight of the all-wheel-drive system is more than overcome by the additional 95 horsepower and 81 foot-pounds of torque from the new, larger engine and the deeper gearing in the silky-smooth, quick-shifting 7-speed transmission.

One drawback for both the V6 and V8 versions is that both of these more powerful engines require premium fuel.

The 5.6-liter V8 engine's sound is muffled back to provide the car with a luxury feel, and the 7-speed double-overdrive transmission certainly lowers engine rpm at highway speeds; nevertheless, the throttle response is extremely quick, and the M56 accelerates with authority. And it does so quietly. This is not the 5.6-liter V8 used in the Nissan pickup trucks. Rather, is a larger version of the Infiniti 5.0-liter V8, the division's first engine fitted with direct fuel injection cylinder heads and other technologies such as variable valve timing and intake valve lift, and a variable intake tract, yielding a combination of low-end torque, high-rpm power, and very good fuel economy for an engine this size in a heavy luxury car.

The M56X has a heavy steering feel aided by its heavier nose weight and tendency to understeer, but it acquits itself quite well on curvy roads, with lots of help from the suspension system, which uses mechanical twin-piston shock absorbers instead of electronic ones. It's plush and sporty at the same time without the harshness added by the 20-inch tires and wheels that come with the Sport package.

We found the braking to be exemplary, with a nice, high pedal, progressive actuation, and excellent ABS performance on panic stops. The standard brakes on our M56X were 12.6 inches front and 12.1 inches rear, but the Sport package brakes are huge: 14 inches front, 13.8 inches rear. Infiniti M brakes come with ABS, Electronic Brake-force Distribution and Quick Brake Assist.

Summary
The 2011 Infiniti M is the newest arrival among luxury sedans starting at $45,000 where German cars are the dominant players. The new Infiniti M looks better, drives better and feels better in every way than the car it replaces, at about a $400 premium for V6 and $2500 premium for the V8 versions. However, there is no more $1300 gas guzzler tax to pay on V8 models. This is a fairly and competitively priced, voluptuously styled luxury car that most drivers would agree wants for nothing in standard form and offers a huge array of options for customizing.

NewCarTestDrive.com correspondent Jim McCraw filed this report from San Diego, California.