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2013 Infiniti M56 review: Infiniti's 420-hp sedan is the opposite of efficient

Even with its clever (and sometimes awkward) Eco Pedal tech, the M Sedan's V-8 struggles at the pump.

Antuan Goodwin
Antuan Goodwin Reviews Editor / Cars

Antuan Goodwin gained his automotive knowledge the old fashioned way, by turning wrenches in a driveway and picking up speeding tickets. From drivetrain tech and performance to car audio installs and cabin tech, if it's on wheels, Antuan is knowledgeable.

9 min read

The Infiniti M37 sedan starts at $48,700, but our 2013 M56 sedan starts at a base price of $63,700. What do you get for the extra $12,500? About 1.9 extra liters of displacement that's about a Honda Civic's worth of engine size and power. That's an impressive little source of bragging rights there, but does it really make this flagship sedan better than its more modest sibling?


2013 Infiniti M56

The Good

The <b>2013 Infiniti M56 sedan</b> packs a very potent level of standard infotainment features and audio sources. The Technology package adds a number of clever and forward-thinking driver aid features.

The Bad

The 420-horsepower sedan simply isn't fun to drive. The Eco Pedal feature is awkward and didn't really help the V-8's efficiency very much.

The Bottom Line

The 2013 Infiniti M56 is plenty powerful, but its true strengths are its safety and its cabin. Save your money and opt for the smaller engine.

420 horsepower V-8
The 5.6-liter V-8 engine that spins its crank under the M56's hood outputs 420 peak horsepower and 417 pound-feet of torque. The engine is mated to a seven-speed automatic transmission, the only gearbox available on the M56, which sends power to the rear axle. Users have the option of upgrading to an all-wheel-drive system, but our vehicle was not so equipped. The transmission features a manual shift mode that is activated by moving the shifter to the left and rocking the lever back for rev-matched downshifts and up for upshifts.

On the center console, drivers will find the Drive Mode Selector knob, with which you can select one of four different driving modes. Sport puts the gearbox into its most aggressive mode, holding each gear longer for peak power and blip-downshifting when braking in preparation for a corner. Eco slightly detunes the output and throttle map and short-shifts each gear for smooth, economical driving. The Eco mode also activates an optional feature called the Eco Pedal, which we'll return to momentarily. Normal is, of course, the baseline performance mode, and Snow optimizes output for maximum traction in slippery conditions.

Our M56 was equipped with a $5,650 Sport package, which bumps the standard 18-inch wheels up to 20-inch, five-spoke rollers shod in stickier, performance tires. Nested in those wheels, you'll find four-piston sport brakes up front and two-pot stoppers on the rear axle along with upgraded sport suspension components with stiffer springs. The Sport package also adds a feature called 4-Wheel Active Steering.

2013 Infiniti M56 sedan: Understated almost to a fault (pictures)

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The 4-Wheel Active Steering system adds a few degrees of steerability to the wheels on the rear axle, working automatically and in tandem with the front wheel's steering. At low speeds, the rear wheels' angle counters the direction of steering to reduce the turning radius and required steering-wheel effort. At high speeds and during lane changes, the rear wheels angle in the direction of steering to increase vehicle stability. At any speed, you probably won't notice that the seamlessly integrated system is actually doing anything.

Finally, the Sport package finishes up with magnesium paddle shifters for easier shifting, sport seats with deeper bolstering, and a number of styling upgrades inside and out to complete the "sport sedan" look.

On the road
If you're looking at the specs -- 420 horsepower, Sport package, 4-Wheel Steering -- and thinking that the M56 is a brute in a suit, think again. I found the M's performance to be largely understated, almost to a fault.

5.6-liter V-8
You pay a lot of extra dough for the M56's larger, V-8 engine. Antuan Goodwin/CNET

The engine doesn't impose itself on the driving experience, most of the raw power being smoothed out by the automatic transmission's smooth shifts -- even in the sportiest mode. The sport-tuned suspension is remarkably smooth and well-damped despite its big ol' wheels and the handling is well-composed and planted. If the 4-Wheel Active Steering system is doing anything, you wouldn't be able to tell from the driver's seat; it's that seamless in its operation.

However, the M56 just doesn't reward the sort of spirited driving that its bright red "S" badge would seem to encourage. The vehicle doesn't hide its size at all and doesn't seem to enjoy being hustled around a corner. Matt the go-pedal and your ears will be treated to a remarkably wheezy engine note -- this does not sound like a 5.6-liter V-8.

I'm not saying that the M56 can't handle itself at high speed, but I found myself having a hard time reconciling paying a base price of over $60,000 for a car that didn't feel more special than a G37 (ahem, Q50) sedan. At the end of the week, I realized that I'd not spent much time driving the M56 fast. With the M37 sedan offering the same level of luxury, I figure that if I'm going to drive slowly, I'd rather skip the V-8 and do it with an extra $12,500 in the bank.

The Eco Pedal
With its Drive mode selector in the Eco position, our Technology package-equipped M56 was able to take advantage of a feature called the Eco Pedal. This feature adds a small motor to the accelerator that can add resistance and movement to the pedal travel. Like most cars' efficiency modes, the M56's Eco mode is able to slightly detune the engine output, adjust the throttle map, and adjust the shift points of the automatic transmission to squeeze a few extra miles per gallon out of the power train. However, with the Eco Pedal active, the M56's computer is able to add resistance to travel to discourage lead-footedness. Give it too much gas and the Eco Pedal will even push back on your foot, recommending haptically that you take it easy.

This Eco Pedal's push-back is easy enough to simply press through for those moments when you genuinely need to get up and go, such as during highway merges or when making a passing maneuver. However, the feeling that the car simply doesn't want to do what you tell it to is unnerving. The driver can adjust the Eco Pedal between two levels of resistance (standard and a reduced setting) and totally defeat it using the touch-panel interface.

Drive selector knob
Place the Drive mode selector into Eco and the optional Eco Pedal will push back on your lead foot. Antuan Goodwin/CNET

I forced myself to stay in the Eco mode for about half of my driving in an attempt to fully test the system, but at the end of the week with the M56, I still found the slight hesitation that the Eco Pedal system can cause and the pedal push-back to be quite annoying. I can understand wanting to eke a few extra miles out of every gallon of fuel, but this technology seems a bit out of place on a 420-horsepower sport sedan with an EPA-estimated 19 mpg combined average. City and highway estimates are 16 and 24 mpg, respectively, but we were unable to crest 13 mpg, even with a heavy emphasis on highway driving for our testing. If you really care about fuel economy, the 5.6-liter variant is probably not the M sedan for you -- instead, take a look at the Infiniti M Hybrid.

Driver aid tech package
The $3,050 Technology package that adds the Eco Pedal also adds an array of other driver aid features.

Blind Spot Warning illuminates a light when an obstruction is in the vehicle's blind spot at speed. Lane Departure Warning sounds a beep when you drift across lane marker lines without using a turn signal. Intelligent Cruise Control maintains a safe following distance when cruising on the highway and Intelligent Brake Assist with Forward Crash Warning watches the road ahead for obstructions, and sounds an alert and preps the brakes when a collision is imminent.

However, tap one button on the steering wheel and these systems all switch from passive alerts to active driver aid systems. Blind-spot and lane departure warnings become intervention systems that can pull the vehicle back in line when you attempt to merge into an obstruction or drift out of your lane. Forward Crash Warning becomes Distance Control Assist.

Forward radar sensor
Many of the Technology package's features rely on the forward radar array in the M's lower grille. Antuan Goodwin/CNET

With the Distance Control Assist system active, the accelerator pedal servo from the Eco Pedal is again called into play. If the system detects that you're approaching a vehicle ahead too quickly and have made no attempt to slow yourself, it will assume that you're not paying attention and gently remove your foot's pressure from the accelerator while applying automatic brake pressure to maintain a safe travel distance -- all the way down to a complete stop if necessary. You can force through the feedback if you really want to hit the car ahead, but I rather liked this implementation of the technology.

The Technology package also adds Adaptive Front Lighting, which steers the headlights into a bend when you turn the steering wheel, and motorized precrash seatbelts for the front seats that cinch up before a collision to hold the occupants in place.

Infotainment tech
You'll notice that the Technology package didn't add any infotainment options to the M56's feature list. That's because the sedan makes almost all of its cabin technology standard features.

8-inch color display
The M56 sedan comes standard with a very respectable level of cabin tech and amenities. Antuan Goodwin/CNET

Even with no option boxes checked, the M56 rolls off of the dealer's lot packing a hard-drive-based navigation system that combines Infiniti Connect with NavTraffic and NavWeather. The navigation system features crisp maps and quick searching for destinations, but I ran into a few hiccups that kept me from loving it. For starters, entering a destination simply involves too many steps. I couldn't understand why a system that is location-aware by nature required me to input my city and state for every address, rather than just returning the nearest results first. Even when using voice input for a street address, Infiniti's system put me through six to seven prompts for each destination. Additionally, while the chosen routes were usually acceptable, on a few occasions, the system seemed to send me out of my way. During one particular trip, the system asked me to drive almost an hour out of my way for a trip to avoid congestion of a bridge and wouldn't provide a shorter route until I eventually ignored the prompts and took the obvious route myself.

The NavTraffic and NavWeather systems are powered by the standard SiriusXM Satellite Radio connections and a three-month subscription is included. The Infiniti Connection service is an OnStar-like telematics system that gives drivers access to automatic collision notifications, remote door unlocking, stolen vehicle recovery, and a host of other connected features, but I mostly used the system to search the Web for navigation destinations not present in the local database. A year of complimentary Infiniti Connection service is also included with the M56 purchase. However, after the Infiniti Connect and SiriusXM trials end, the M Sedan's driver will be responsible for maintaining two separate subscriptions to keep the same level of infotainment functionality that the car rolled off of the lot with. It's a shame that all of that data can't just be piped through the single Infiniti Connection data stream.

The standard list of audio sources includes SiriusXM Satellite Radio, AM/FM radio, a single-disc CD player, USB connectivity for mass storage devices, iPods, and iPhones, and Bluetooth connectivity for hands-free calling and audio streaming. That's pretty much every source that we could ask for outside of HD Radio, but I don't think that anyone will lose too much sleep over that omission.

The standard audio rig is a 10-speaker Bose stereo system, but the aforementioned Sport package bumps our M56 up to a 16-speaker, 5.1 surround-sound premium Bose Surround system. Audio quality is good, but also nothing to get too excited about. I noticed quite a bit of low-end distortion in the bass and a bit of rattle coming from somewhere in the cabin even at moderate volumes.

Other standard niceties include a rearview monitor, a sonar-based rear proximity system, HID headlamps, eight-way power-adjustable front seats with heated and ventilated surfaces, and Intelligent Key entry with push-button start.

In sum
As stated earlier, the 2013 Infiniti M56 starts at $60,600. Our tester was equipped with the Technology and Sport Packages which, when added to the $895 destination charge, bump the as-tested price up to $70,195. Now that price is lower than a comparably equipped Lexus LS 460 or a BMW 550i, but I'm not sold on the value.

Infiniti M56
The Infiniti M56 may boast high horsepower, but it doesn't feel more much more capable than its less powerful siblings. Antuan Goodwin/CNET

It's a capable car, but the M56 isn't particularly fun to drive. It's not particularly efficient either, despite the awkward Eco Pedal gimmickry. Most other automakers are moving to smaller, more efficient turbocharged V-6s for their most powerful offerings while Infiniti presses on with this big ol' V-8 for its high-tech flagship. In fact, the best parts of the M56 -- its strongest advantages -- are the safety features that are available in the Technology package. And if that's what you're interested in, I'd suggest that you take a long look at the M Hybrid and M37 and honestly ask yourself, "Do I really need 420 horsepower?"

Tech specs
Model 2013 Infiniti M56 sedan
Trim Technology and Sport packages
Power train 5.6-liter V-8 engine, seven-speed automatic transmission, rear-wheel drive
EPA fuel economy 16 city, 24 highway, 19 combined mpg
Observed fuel economy 13.1 mpg
Navigation standard HDD navigation with NavTraffic/NavWeather and Infiniti Connection
Bluetooth phone support standard
Disc player single-slot CD
MP3 player support standard analog 3.5mm auxiliary input, USB/iPod connection, Bluetooth audio streaming
Other digital audio SiriusXM Satellite Radio
Audio system 16-speaker Bose Surround premium audio
Driver aids Blind Spot Monitoring and Intervention, Lane Departure Warning and Intervention, Distance Control Assist, Forward Collision Warning, Adaptive Front Lighting, rearview camera, rear proximity sensor
Base price $60,600
Price as tested $70,195


2013 Infiniti M56

Score Breakdown

Cabin tech 8Performance tech 6Design 8


Available Engine GasBody style Sedan