CHULA VISTA, CA – Infiniti’s new ’11 M sedan presents a great mix of ridiculous power, astonishing fuel economy and parental-like controls sure to please, and perhaps perplex, buyers.

The M cranks out a whopping 420 hp and 417 lb.-ft. (565 Nm) of torque from its new 5.6L V-8. But thanks to direct-injection technology and other fuel-sipping features, we were able to average an astonishing 28.2 mpg (8.3 L/100 km) on one test route here.

While some may think it sacrilege for a sport sedan, Infiniti has introduced an Eco mode and optional Eco pedal on the new M.

Much like mom would do, both Eco technologies remind drivers, “Geez, Louise, ease off the gas.”

Other technologies, many of which can be turned off, suggest drivers “Pay attention, for Pete’s sake!”

Distance-control assist slows the vehicle when cameras and sensors detect the M getting too close to another car for comfort.

The M also can steer and apply the brakes when a driver drifts out of his lane (lane-departure prevention) or tries to move into a lane occupied by another vehicle (blind-spot intervention).

The ’11 Infiniti M, on sale March 18 in the U.S., offers Nissan’s 3.7L V-6 from the current G lineup and the new 5.6L V-8 that replaces the 4.5L V-8 in the soon-to-depart M45.

Both mills are mated to a 7-speed automatic transmission with manual shift mode.

The new M37’s 3.7L V-6 makes 330 hp and 270 lb.-ft. (366 Nm) of torque, up from 303 hp and 262 lb.-ft. (355 Nm) of torque for the outgoing M35’s 3.5L V-6.

The M37, which should account for the vast majority of sales, has a different personality from its larger-mill brother. Although its exhaust note is buzzy, the car feels more ready-to-run than the M56, with quicker throttle and shift responses in Sport and Standard driving modes.

Noise, vibration and harshness issues detected with the 3.7L in the G is muted in the bigger M. Infiniti’s Active Noise Control, which uses the M’s sound system to cancel out unwanted engine racket, may play a role in that improvement.

A standard center-console dial allows all ’11 M drivers to choose between four modes: Sport, Standard, Eco and Snow. Each has unique throttle and transmission settings.

The concept of different drive settings, a burgeoning trend industry-wide, is a good one. Most people are unable to utilize 420 hp, or 330 hp for that matter, in daily driving, so offering a setting that prioritizes fuel economy in large vehicles makes sense.

The rear-drive M56 is the better suited of the two models for comfort cruises, with a deeper, less noticeable exhaust note.

While it does present a more aggressive throttle tip-in than the ’10 M45, which doesn’t let loose until half-open throttle, the calibration feels timid compared with the M37 or the Hyundai Genesis sedan.

In aggressive driving over hilly terrain in the M56, with speeds between 30 and 50 mph (48-80 km/h), we average 20.6 mpg (11.4 L/100 km) in Sport mode. In Eco mode and with Eco pedal, the M56’s fuel economy jumps to 28.2 mpg (8.3 L/100 km) with non-aggressive driving at similar speeds.

That figure is better than the 26.8 mpg (8.8 L/100 km) returned in an M37, in Eco mode and with Eco pedal, on the same route and at the same speeds.

’09 ’11 Infiniti M56 RWD
Vehicle type Front-engine, rear-drive, 5-passenger sedan
Engine 5.6L DOHC all-aluminum DI V-8
Power (SAE net) 420 hp @ 6,000 rpm
Torque 417 lb.-ft. (565 Nm) @ 4,400 rpm
Bore x stroke (mm) 98.0 x 92.0
Compression ratio 11.5:1
Transmission 7-speed automatic
Wheelbase 114.2 ins. (290 cm)
Overall length 194.7 ins. (494 cm)
Overall width 72.6 ins. (184 cm)
Overall height 59.1 ins. (150 cm)
Curb weight 4,028 lbs./1,827 kg
Base price $57,550 ($46,250-$60,050 range for all Ms)
Fuel economy 16/25 mpg (14.7-9.4 L/100 km)
Competition BMW 5-Series, Audi A6, Mercedes-Benz E-Class, Lexus GS, Cadillac STS
Pros Cons
420 hp, 417 lb.-ft. Not for everyday use
28 mpg Eco tech annoying
4-wheel Active Steer 4-wheel Active Steer

Eco pedal causes the throttle to resist even moderate acceleration demands when in Eco mode, pushing back on a driver’s foot. The sensation is annoying, and the pedal resistance extreme, when trying to travel uphill – you will get passed by other vehicles. But for 28.2 mpg in a huge sedan, it’s worth it.

All Ms continue to boast a double-wishbone front and multi-link independent rear suspensions. However, rear-suspension geometry is changed and laser welds are added to the mounting points to boost stiffness and provide a quieter, more composed ride.

Also reining in the rear of the M is Infiniti’s 4-wheel Active Steer (4WAS) system, which turns the rear wheels in phase with the front wheels up to 1 degree to keep the car planted when cornering.

The extra control 4WAS provides is appreciated, but it does prevent the M from completely letting down its hair.

While it’s never easy to make a big car sexy, Infiniti designers did a good job sculpting the front of the sedan, its deep curves eliminating some of the visual heft that plagues the ’10 Ms.

The new model also is upgraded on the inside, with Infiniti doing a better job of disguising the few regrettable touches of hard-plastic trim (such as on the steering column) that remain by giving the material a nice gloss and tecture.

Aluminum and leather trims are of superior quality, as is a velvety fabric headliner.

Silver-like particles on the upgrade ash-wood trim lend a cool effect, but the highly lacquered finish gives it a dated appearance compared with the matte-finish woods many auto makers now employ.

The curvaceous lines of the exterior are repeated inside the car to great effect, most notably on the doors. From a distance, the aluminum and wood door-handle surround has the appearance of an elongated eye with mascara-covered lashes.

Ergonomically, the M is an easy car to love. The protruding center stack puts all buttons within reach, even the sound system tuning knob, essential for skimming through voluminous satellite radio stations and positioned on the far right. The curled interior handles not only are visually stunning but easy to grip.

Roominess abounds both front and rear, but seating comfort is middle of the pack. Longer drives called unwanted attention to cushion firmness.

The M offers four well-appointed grades: M37 RWD; M37x (all-wheel drive); M56 RWD and M56x, all with standard leather seating and 10-way power driver and front-passenger seats.

Upgrades include navigation with an 8-in. (20-cm) touch screen and 10-speaker Bose stereo.

The ’11 M is an impressive automobile, thanks to its power, fuel efficiency and advanced safety technologies.

U.S. government statistics show nearly 6,000 people were killed and more than 500,000 injured as a result of distracted drivers in 2008.

With that in mind, a car that can brake and steer itself out of harm’s way certainly qualifies for Mom’s seal of approval.

cschweinsberg@wardsauto.com