Used 2012 INFINITI M Sedan

The 2012 Infiniti M is the most sporting in its segment of premium sedans, but its firm ride might be a turn-off for luxury-minded buyers seeking a more gracious driving experience.

The 2012 Infiniti M aspires to be both a luxury car and a sport sedan. This can be a difficult balance to strike, as shoppers in each of these segments often have opposing expectations. Sport-sedan shoppers usually prize a car that offers visceral engagement, whereas the average luxury-car shopper seeks a more gracious driving experience. In the end, the M delivers a mix that favors sport-sedan territory; it's the most performance-oriented choice in its segment, blending opulent accommodations with brawny engines and keenly attuned handling.

Available with rear-wheel drive or all-wheel drive, the M comes with a choice of three powertrains. Pleasingly, there isn't a dud among the bunch. The M37 has the smallest engine of the trio, a 3.7-liter V6 good for 330 horsepower, a rating that makes it more powerful than any other V6 in its class. At the top of the range is the M56, whose 5.6-liter 420-hp V8 makes it, like the M37, one of the most muscular choices in its segment.

Sitting between these two on the power spectrum is the new M Hybrid. The Hybrid combines a 3.5-liter V6 with an electric motor for a total of 360 hp. As with most other hybrid models, the M35h is a full hybrid, which means it can move under electrical power alone (up to 62 mph, says Infiniti, though that's likely with a very light foot). Electrical power is stored in a lithium-ion battery pack, and this in turn helps the M35h achieve both V8-like acceleration and fuel economy comparable to that of a four-cylinder sedan.

In addition to prodigious power, the M also offers a wide array of cutting-edge technology. You'll find comfort features like the Forest Air purification system, designed to guide air flow within the cabin so it resembles that of a gentle breeze, and performance features like Active Trace Control, which enhances the transition from braking to acceleration through corners. Meanwhile, the usual convenience and comfort amenities live in a cabin rich with handsome design and superior materials.

The M's biggest flaw is its ride quality, which might be too firm for some luxury-minded shoppers (especially when fitted with the Sport package). Though the Infiniti M has sporting intentions, rivals like the 2012 BMW 5 Series and 2012 Mercedes-Benz E-Class react to the road with more refined manners. The technology-oriented 2012 Audi A6 and affordably priced 2012 Hyundai Genesis are also worth checking out. But for shoppers interested in a luxury sport sedan that puts "sport" front and center, the M presents the most involving game in town.

The 2012 Infiniti M is a midsize luxury sedan available in three trim levels: M37, M35h and M56.

Standard on the M37 are 18-inch alloy wheels, automatic bi-xenon headlights, foglights, power-folding heated mirrors, automatic wipers, a sunroof, keyless ignition/entry, dual-zone automatic climate control, leather upholstery, heated eight-way power front seats, power lumbar support, driver memory functions, a power tilt-and-telescoping steering column and an auto-dimming rearview mirror. Also standard are a rearview camera, Bluetooth and a six-speaker stereo with a CD player, auxiliary audio/visual jack, an iPod interface and satellite radio.

The M56 adds a navigation system, real-time traffic/weather updates, voice recognition, heated and ventilated front seats, a heated steering wheel and a Bose 10-speaker premium audio system with digital music storage.

With the M35h, you get all the standard features offered with the M37, along with a hybrid powertrain, regenerative braking and unique instrument meters and display screens. You also get Infiniti's Vehicle Sound for Pedestrians (VSP), which compensates for the silent electric motor by generating a range of distinctive sounds designed to alert other road users to the car's presence.

Both the M37 and M35h are available with a Premium package that adds heated and ventilated front seats, a heated steering wheel, a navigation system (with voice control, real-time traffic and real-time weather) and a 10-speaker Bose stereo with streaming Bluetooth audio and digital music storage. The Deluxe Touring package adds a power rear sunshade, an in-car air purifier, upgraded leather upholstery and interior trim, and a 16-speaker Bose surround-sound stereo.

The M37 and M56 each offer a Sport package, although the content varies between trims. The M37 package includes 20-inch wheels, summer tires, sport-tuned suspension and brakes, four-wheel active steering, sport seats and steering wheel, and unique exterior styling elements. The M56 package includes the M37 features and adds a power rear sunshade, a Bose surround-sound stereo and an in-car air purifier; these additional amenities can also be purchased for the M37 as a Sport Touring package.

Buyers who choose the M's Technology package get adaptive cruise control, a lane departure warning and prevention system, a blind-spot warning system, a forward collision warning system, adaptive headlights and the "eco pedal" that provides feedback to the driver to encourage fuel-efficient driving.

The Infiniti M37 is powered by a 3.7-liter V6 that produces 330 hp and 270 pound-feet of torque, while the M56 is motivated by a 5.6-liter V8 that produces 420 hp and 417 lb-ft of torque. The M35h runs on a hybrid powertrain and offers a combined 360 hp from its gas-fueled 3.5-liter V6 and electric motor. Rear-wheel drive is standard, and the M37 and M56 are available with all-wheel drive. A seven-speed automatic transmission is standard on all three models and has four different shift modes (Standard, Sport, Snow or Eco).

In Edmunds performance testing, the M37 went from zero to 60 mph in 5.9 seconds, while both the M56 and M35h made the same sprint in a very impressive 5.2 seconds. With rear-wheel drive, the M37's EPA-estimated fuel economy is 18 mpg city/26 mpg highway and 21 mpg combined, with the rear-wheel-drive M56 logging 16/25/19. Estimated mileage for the M35h is an impressive 27/32/29.

The 2012 Infiniti M37 comes standard with antilock brakes, stability and traction control, front side airbags, side curtain airbags and active head restraints. Included in the Technology package are a lane-departure warning and prevention system, blind-spot warning system and a forward collision warning system with intelligent brake assist. All three M models did very well in Edmunds brake testing; the M37 stopped in 115 feet, the M35h in 119 feet and the M56 in 112 feet.

In government crash testing, the M37 earned an overall rating of four stars out of a possible five, with four stars for overall frontal crash protection and five stars for overall side crash protection. The Insurance Institute for Highway Safety gave both the M37 and M56 the best possible of rating of "Good" in the frontal-offset, side and roof strength tests.

The 2012 Infiniti M is a big car, but drives smaller than you might think. Its steering weights up less abruptly than that of other Infiniti and Nissan sedans, and it exhibits a downright feline willingness to change direction. All three powertrains offer the sort of abundant power and acceleration that makes them standouts in their segments.

Those wishing for an even more sharply tuned luxury sedan can select the Sport package's various performance upgrades. The combination of a sport suspension and 20-inch wheels, however, results in a firm ride that won't suit many buyers in the luxury segment.

Infiniti has given the M top-notch cabin design and high-quality materials. As with the car's exterior styling, the cabin's powerful lines call to mind the muscular curves of a bodybuilder flexing on the podium. Opting for the Deluxe Touring package adds seats upgraded with diamond-quilted leather and contrasting piping, unique "silver-powdered" wood trim, a faux-suede headliner and enhanced material on most primary touch points. In total, the M's interior challenges those of its established European rivals for refinement.

It also has the space and technology to compete with the Europeans as well. The cabin is quite roomy, offering generous space for occupants and a relatively tall greenhouse that provides good outward visibility. As for technology, it's hard to think of a rival that betters the M for all the available entertainment, comfort and safety technologies that can be had once you check all the options boxes. In particular, Infiniti's navigation and audio interfaces are some of the most user-friendly in the business. In terms of storage, the M has a 14.9-cubic-foot trunk; that drops to 11.3 cubic feet for the M35h.