CNET logo Why You Can Trust CNET

Our expert, award-winning staff selects the products we cover and rigorously researches and tests our top picks. If you buy through our links, we may get a commission. Reviews ethics statement

2011 Infiniti M56x review: 2011 Infiniti M56x

2011 Infiniti M56x

Wayne Cunningham Managing Editor / Roadshow
Wayne Cunningham reviews cars and writes about automotive technology for CNET's Roadshow. Prior to the automotive beat, he covered spyware, Web building technologies, and computer hardware. He began covering technology and the Web in 1994 as an editor of The Net magazine.
Wayne Cunningham
7 min read

Photo gallery:
2011 Infiniti M56x


2011 Infiniti M56x

The Good

With unique features such as Forest Air and Distance Control Assistance, Infiniti keeps its 2011 M56x on the cutting edge of automotive technology. Its blind spot detection and lane-keeping assistance are useful driver aids. Also, its audio, navigation, and Bluetooth phone systems are all first rate.

The Bad

To really compete in the luxury class, Infiniti should give the M56x a more comfortable ride. The M56x's voice-command structure is too complex and if it had paddle shifters, sport driving could be more fun.

The Bottom Line

The 2011 Infiniti M56x excels in its driver aid features and standard cabin tech, but it falls just a little short of its bigger luxury competitors in stately elegance.

Although Infiniti makes an upscale distinction from Nissan with vehicles like the G37 and FX35, its top-of-the-line M sedan never came up to the stately luxury of flagship sedans from BMW, Lexus, and Mercedes-Benz. For 2011, Infiniti updates its M56x to push power and interior quality substantially higher than what previous versions had, but it's still not at a level where we would suggest hiring a chauffeur.

In fact, with its Technology package, there seems little need for a driver at all. Not only does the M56x sound an alert if the driver lets the car drift across lane lines, it also has offside wheel braking, which is just a pulse, that helps to nudge the car back into its own lane. If the car detects the traffic ahead of it start to slow down, the M56x applies the brakes, bringing itself to a full stop. Just about the only thing the Infiniti won't do is time travel to 1984 and hunt down Sarah Connor.

Infiniti pioneered these groundbreaking driver assistance technologies, and the M56x benefits by getting the full suite. We have tested adaptive cruise control systems in different Infiniti models as well as cars from other automakers. With this feature active, we drove the M56x down the freeway, set the speed, and watched as it slowed down automatically when approaching traffic. One issue we noticed with Infiniti's system is that when a car cut in front of us, the radar would lose its lock, and the M56x would immediately lift up on the gas and slow dramatically until it regained a radar lock. We understand why Infiniti programmed it this way, but the driver behind us probably didn't.

You can turn DCA on or off with a steering-wheel-mounted button.

Distance Control Assistance and its associated Intelligent Braking work like adaptive cruise control, hitting the brakes on the M56x for traffic stopped or slowing ahead. This system is a little more controversial, as it pushed back on the gas pedal when we approached stopped traffic, making us feel like we were fighting with the car. In dense city traffic, it was problematic, because it brakes and stops the M56x a full car length behind other cars, but in lighter suburban traffic that kind of stopping distance would be more acceptable.

Ultimately we learned to work with DCA, resisting the gas pedal push-back so we could tuck in closer to stopped traffic. This technology will prove useful for perpetually distracted drivers, preventing rear-end collisions. However, we also found that it seemed to get a lock on traffic ahead only about 50 percent of the time, so we couldn't always rely on it to stop the car. DCA feels like a tech novelty at this point, and is not turned on by default.

Active Eco mode
Another unique tech feature on the M56x, which also might prove to be controversial, is its Eco mode. Rather than merely dial down accelerator response and show economy performance on the dashboard, as other systems do, Infiniti's Eco mode adds resistance to the gas pedal, making it harder to push. We found we could push through the resistance to get a more satisfying start, but following the pedal's dictates made 0-to-25-mph runs take more than 10 seconds.

This dial switches the drivetrain mode between Snow, Eco, Normal, and Sport.

Infiniti instituted Eco mode in the M56x because the car's new V-8 is the biggest engine yet in an M sedan. This monster displaces 5.6-liters to generate 420 horsepower and 417 pound-feet of torque, putting the M56x on par with luxury competitors. Although Infiniti uses a technology it calls Direct Injection Gasoline to control the injectors, this car uses standard port injection, not the direct injection into the cylinders that other automakers are using.

At 16 mpg city and 23 mpg highway, the M56x's fuel economy isn't terrible considering its engine size, but it might be improved through true direct injection. We turned in a fuel economy of 17.6 mpg, with the car's seven-speed-automatic transmission proving crucial for raising the average during freeway travel.

Lacking a dedicated sport mode, the automatic transmission sets the tone for this luxury cruiser. It did just fine on the road, downshifting readily when we hit the gas, and keeping the engine speed low at freeway speeds. But no sport mode or paddle shifters for the manual suggest the M56x isn't designed for power cornering. The transmission's manual mode seems more suited for hill descents.

With seven speeds, the automatic transmission helps keep freeway fuel economy high.

However, the same dial that turns on Eco mode also has a setting for Sport. This setting dials up the responsiveness of the gas pedal. Think of it as anti-Eco mode. In Sport mode, the car delivers very satisfactory acceleration. During fast starts, the M56x leaped forward willingly and proceeded with a fairly smooth acceleration curve.

Just about every Infiniti or Nissan vehicle shows at least better-than-average handling, and the M56x maintains this tradition. It doesn't have the sports car tightness of the G sedan or the Nissan 370Z, but the car does resist body roll in the turns as well as the BMW 750i does.

With its conventional suspension system, there is no way to change the ride quality for different driving conditions. As such, its firmness became evident as we drove over rougher surfaces. This is one area where the M56x doesn't quite measure up to the luxury competition, as it didn't mask out bumps and pits in the road as well as it should.

Refined interior
Similarly, the rear seat doesn't offer the legroom that its luxury competitors do. The M56x has a very nice cabin, and we had no problems with the quality of the interior materials, especially the silver-flecked wood trim. But the rear seat space felt a bit compact, more comparable to a BMW 5-series than a 7-series. Until Infiniti makes a stretched M, the brand will lack a true flagship sedan.

This new control knob looks sleeker than Infiniti's previous version.

The car's occupants benefit from Infiniti's excellent cabin tech package. We've always liked Infiniti's navigation and audio control system, which combines a multidirectional knob with touch-screen action. For the new M56x, Infiniti refined that knob, making it look more at home in a luxury interior without losing any of the functionality.

The hard-drive-based navigation system's rich maps show 3D renderings of a few landmark buildings in some downtown areas. The points-of-interest database includes Zagat-ratings for restaurants, although its interface is terrible. To find restaurants in the San Francisco area, we had to scroll past every region that began with a letter before S. The system should just show a list of every nearby Zagat-rated restaurant.

The system overlays traffic information on its maps, showing trouble spots, and dynamically routes around them. Route guidance proved very usable, with explicit graphics showing turns and voice prompts that pronounce the names of streets.

As our M56x had the Deluxe Touring package, it came with a unique Infiniti touch, speakers on the seat shoulders. The Bose-branded audio system in the car uses 16 speakers, with four in the front seat shoulder positions and another six in the front doors. That leaves two on each rear door, plus a center fill and a subwoofer. Of course, a system like this supports 5.1 surround sound, and we enjoyed its immersive experience.

Bose speakers in the seat shoulders contribute to the surround sound effect.

The sound quality was rich and nicely detailed, with a good balance between bass, mid, and high frequency response. Its main fault was some minor door rattle during bass notes.

The stereo gets audio from a good selection of sources, including a USB for iPod integration or USB drives, and Bluetooth streaming audio. Infiniti finally removed the Compact Flash card it used in the earlier generation of this car. You can also use the CD/DVD player to rip music to the onboard hard drive, which has 9.3GB available for music.

The M56x gets a new feature called Forest Air, a nice little trick that varies the air-conditioning fan speed. The intent of this feature is to create the sensation of a forest breeze rather than the steady wind produced by standard air-conditioning systems. With Forest Air set in its fast mode, the fan deviation happened too quickly for us to notice much of a difference, but in its low-speed mode, it worked as advertised, adding a nice atmospheric effect to the cabin.

Infiniti also advanced the Bluetooth phone system it includes in the M56x, adding a voice command dial by name feature. We had mixed results using the system. First, the voice command structure is a little strained, requiring us first to say "phone," then say "handset phone book" before getting to the point where we could tell it to call a specific name. While parked, the system worked fine; however, when we were driving, we had a hard time getting it to understand names on a paired phone.

In sum
The 2011 Infiniti earns its highest score for cabin tech, as the car not only comes with a solid cabin tech suite, but it also pioneers some driver-assistance features not seen before. The Forest Air feature of the climate control is also a nice touch. The exterior and interior design, down to the cabin tech interface, is also quite good. Infiniti has established its own design language that uniquely identifies the car. As for performance tech, we like the seven-speed automatic transmission, and the Eco drive mode is very intriguing. But the engine isn't particularly advanced, primarily relying on big displacement for power.

Spec box

Model2011 Infiniti M56x
Power train5.6-liter V-8
EPA fuel economy16 mpg city/23 mpg highway
Observed fuel economy17.6 mpg
NavigationHard drive-based with traffic
Bluetooth phone supportStandard
Disc playerMP3 compatible CD/DVD player
MP3 player supportiPod integration
Other digital audioOnboard hard drive, USB drive, auxiliary input, Bluetooth streaming audio, satellite radio
Audio systemBose 16 speaker 5.1 surround system
Driver aidsRearview camera, blind spot detection, lane departure warning, lane departure prevention, adaptive cruise control, distance control
Base price$60,050
Price as tested$68,260

2011 Infiniti M56x

Score Breakdown

Cabin tech 9Performance tech 7Design 8


See full specs Available Engine GasBody style Sedan