The sticker prices land right on top of one another and so do the performance figures: $73,400 for the 420-horsepower, rear-drive Infiniti M56 Sport mid-size sport sedan, versus $73,300 for the 400-hp BMW 550i with rear-wheel drive. And both will do 0-100 km/h in less than 5.5 seconds.
The similarities do not end there. Both are powered by sizable V-8 engines, though the Bimmer has a twin-turbo hooked to an eight-speed automatic transmission. The Infiniti has a normally aspirated V-8 with a seven-speed automatic. These two sedans are also about the same size, are marketed with seriously sporty intent and are equipped with most of the same features.
Yes, it's a head-to-head competition here, with the Infiniti the underdog trying to put a bruising on the 5-Series, which has been ruling this class of car for decades. The 5 has been an exquisite success story for BMW thanks to its uncanny ability to satisfy gearheads and anyone else looking for a luxury sedan with German cachet.
The all-new twin-turbo 2011 BMW 550i is, as you'd expect, a delight. However, the all-new 2011 Infiniti M56 is a thoroughly redesigned sedan and is a worthy contender.
It all starts under the hood, of course. Turbocharged engines are quickly becoming the norm at BMW and the latest to get this treatment is the 550i with its direct-injected, 4.4-litre, twin-turbo V-8. The genius of this engine is the massive torque curve: 400 hp at 5,500 rpm and 450 lb-ft of torque from 1,750 to 4,500 rpm. What's missing is the old V-8's rumbling exhaust, replaced by a less-than-thrilling muted growl. We like the engine anyway.
Drivers suffer no such longing with the Infiniti, especially when it approaches redline. The 5.6-litre V-8 is good for 420 hp at 6,000 rpm and 417 lb-ft of torque at 4,400. Like the Bimmer, it utilizes direct-injection and variable valve timing and valve lift to squeeze out performance.
Both are fine engines, but we'll give the nod here to the BMW for its wide power band and instant responses. The M56's power is concentrated at higher engine speeds. The Infiniti may sound more like a sport sedan than the BMW, but the BMW's powerplant feels as though it responds like the monster it truly is.
Still, various timed runs reveal the Infiniti is actually slightly quicker for the 0-100 km/h dash - perhaps by one- or two-tenths of a second. Why? Heft, most likely. The 550i carries about 100 kg of extra ballast versus its Japanese rival. In fact, the 550i is a rather portly 1,981 kg. This is "EfficientDynamics?"
When it comes to the transmission, we'll give the nod to Infiniti even though it offers one less ratio than the BMW's eight-speed. Infiniti's four driver-controlled modes allow you to manage transmission and throttle mappings. In Manual mode the driver manages shifts via steering-column-mounted magnesium paddle shifters.
The Infiniti is superior because control is fully with the driver; the transmission will neither shift up nor down without being cued by the paddle shifters. Downshift under braking and it rev matches, too.
The BMW is also easy to shift when you want to take control of the gears yourself and it blips the throttle when you grab a lower gear to match revs. However, even in full manual mode, a stomp on the gas will call up a multi-gear downshift. Moreover, if you hit the redline, you get the next cog automatically. So there is a driving nanny at work here. In a sports sedan? No, thank you.
The M56 feels quicker to respond when pushed through corners at a high rate, too. We suspect this is a function of the BMW's mass, also - and the relatively softly sprung suspension even in its firmest mode. The 5's electric power steering feels just a little artificial, too.
The Infiniti variable-assist steering, combined with four-wheel active steering (the rear wheels are turned in phase with the front wheels, depending on vehicle speed and steering angle) isn't quite right, either. In particular, an overly quick turn-in at low to medium speeds can be jarring.
We'd argue the M56 is the preferred ride for aggressive, enthusiastic driving, though the stiff, nonadjustable suspension can make a daily commute tiresome. The BMW is entertaining on curvy roads, but the ride is more plush in the day-to-day driving shuffle.
Then there are the respective cabins. The 550i has the better seats for overall comfort, though the Infiniti has better lateral support. The BMW has more rear head room, while the M56 is richer in back.
Both look and feel luxurious inside; no complaints about the quality of workmanship anywhere. For the most part, I prefer the Infiniti's controls; they are more intuitive and easier to decipher. The tipping point: the 550i has iDrive Version 4 and it remains not entirely intuitive. The M56 gets the clear nod for delivering a modern and stylish look, as opposed to BMW's rather clinical take on cabin design.
The winner, then? For 24/7 enjoyment and comfort, the 550i wins. The M56 is a better performer when pushed hard, but the BMW is no slouch and it is does not wear you out when you're feeling less than frisky.
Infiniti is pretty close, though. Look in the rearview mirror, BMW. That's Infiniti on your bumper.
2011 BMW 550i
2011 Infiniti M56 Sport
Mid-size luxury sedan
Mid-size luxury sedan
$73,300 ($800 freight)
$73,400 ($1,920 freight)
4.4-litre V-8, turbocharged
400 hp/450 lb-ft
420 hp/417 lb-ft
Fuel economy (litres/100 km)
12.7 city/7.9 highway; premium gas
12.9 city/8.0 highway; premium gas
Infiniti M56, Audi A6, Mercedes-Benz E-Class
BMW 5-Series, Audi A6, Mercedes-Benz E-Class.
8.0 - The 5-Series is a downsized version of the latest 7-Series and that's not necessarily a bad thing. The current 7 is well-proportioned, with clean lines and an overall balanced look. But the 5 is not a daring design. BMW is back to styling cars as though they are the same sausage cut into different lengths.
8.5 The M56 looks modern and also snarly and aggressive. It's a performance sedan that looks like a performance sedan.
7.5 - Comfortable, yes, and the seats are spectacularly supportive other than for a lack of lateral support. The materials are first rate and they are put together well. But the controls could be more intuitive.
8.5 A very interesting and thoughtful cabin design, with controls that are relatively easy to decipher and seats with excellent lateral support. And all the materials look expensive and modern.
8.5 - Though slightly softer than you might expect, the overall ride quality is very good. The 550i is entertaining, but not punishing. The steering needs to be better connected to the driver, however.
7.0 Sure, the M56 is a delight when you're feeling frisky and you're in the mood to carve corners. But it's a firm ride in the day-to-day commute, and a tiring one, too.
9.0 - Lots of safety gear.
9.0 Lots of safety gear.
5.5 - A twin-turbo sports/luxury sedan is not going to win any Earth Day awards. Worse, the 550i is portly for a car that is supposed to be based on the concept of EfficientDynamics.
5.5 Like its BMW rival, the M56 will not win prizes for fuel economy and it was never intended to do so.
8.5 There are many reasons why the standard for this corner of the market is, arguably, the 5-Series. The 550i is well executed and delivers solid value for the money.
8.0 The M56 is aimed at the hard-core driving enthusiast. Its growly V-8 is quite something, and the paddle shifters deliver ultimate control.
You'll like this vehicle if:
You want to drive an all-around sporting sedan with German cachet.
You are hard-core about your driving and want a luxury sedan with some room and some serious style.