The 2011 Infiniti M37 and M56 replace the 2010 M35 and M45. The difference in name reflects switches to a 3.7-liter V-6 and a 5.6-liter V-8, both of which provide more power, as you'd expect. Many other upgrades come with this complete redesign.
Though beautifully styled inside and outside, the redesigned 2011 Infiniti M sport sedan is frustrated by some quirks and glitches, and it's not as affordable as it used to be.
The M comes in three versions: the M37, M56 and an all-new hybrid version, the M35h. The gas-only versions are rear-wheel drive but offer optional all-wheel drive (designated by the "x" suffix). Unlike some competitors, including the BMW 5 Series and Acura TL, the M sedan doesn't offer a manual transmission. We tested the M37x and both the M56 and M56x, but did not drive the M35h.
Transmission Misbehavior
Though the car impresses, its sport-sedan billing leads me to start with my main complaint: The seven-speed automatic transmission has a chronic case of indecision. Stomp on the accelerator from a standstill, and all is well. Ditto for normal, sedate driving. But when the time comes to pass or get moving more quickly once you're already in motion, the car bogs down as the transmission hunts for a gear.
In this regard, Infiniti's earlier five-speed automatic was better. This pattern is all too familiar: Automakers make the change to higher gear counts for their automatic transmissions — for all of the undeniable benefits — and then the immediacy of the accelerator response suffers, an unacceptable and unnecessary tradeoff.
I cited similar frustrations with the competing BMW 535i's new eight-speed automatic, but the problem is more pronounced in the M37. Further, BMW's V-8 version, the 550i, performed much better, while the M56 exhibits the M37's same bad habits.
Unless you're content to take over shifting responsibility using the transmission's manual mode and gear selector (or shift paddles that come with the optional Sport Package), the best mitigation is the Sport mode on the center console's Infiniti Drive Mode Select knob. Along with making the accelerator pedal more sensitive, it makes the transmission hold onto lower gears longer, cutting down on the delay. But that also serves to decrease the M56's mileage, an already unimpressive 16/23 mpg city/highway with all-wheel drive or 16/25 mpg without. The M37x is rated 17/24 mpg, and the M37 is 18/26 mpg. The M35h hybrid gets an estimated 27/32 mpg.
Midsize Luxury Sedan MPG*
Six-cylinders City, 2WD (AWD) Highway, 2WD (AWD) Combined, 2WD (AWD)
2011 Infiniti M37 18 (17) 26 (24) 21 (20)
2011 BMW 535i 20 (19) 30 (29) 24 (23)
2012 Audi A6 25 (19) 33 (28) 28 (22)
2011 Mercedes-Benz 17 (17) 24 (24) 20 (19)
E350
Eight-cylinders City, 2WD (AWD) Highway, 2WD (AWD) Combined, 2WD (AWD)
2011 Infiniti M56 16 (16) 25 (23) 19 (18)
2011 BMW 550i 17 (16) 25 (24) 20 (18)
2011 Mercedes-Benz 15 (15) 23 (23) 18 (18)
E550
*Automatic transmissions
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