Atop the Infiniti lineup lives the mighty M. Available with a brawny V8 in the M45 or still strong V6 engine in the M35, and offering rear-wheel drive or all-wheel drive, it blends sporty performance with the luxury features buyers crave in a midsize premium car.
My Liquid Platinum M45 tester flaunted the potent 4.5-liter V8, with 325 horsepower and 336 lb.-ft. of torque. Its sophisticated engine features titanium valves, a microfinished crankshaft and slick single-stage cam drive chain, among other advantages, helping it run down the road in a big, silent hurry.
The M's engine also uses variable length air induction and a continuously variable valve timing control system, all in the name of efficiency and smooth power delivery.
You get a lot, but it'll cost ya. I recorded an average of 15 miles per gallon, and the EPA rates the M45 at 16 City, 21 Highway. EPA Green Vehicle ratings are a midpack 6 for Air Pollution and 4 for Greenhouse Gas. But that's not why folks buy an M45 anyway.
The M35's smaller 3.5-liter V6 still puts out a generous 303 horsepower and 262 lb.-ft. of torque. How far we've come that a 300-horsepower sedan is now the lesser model.
All M45s use electronic automatic transmissions. This year, they get the Drive Sport (DS) shift mode, adding more acceleration feel and what Infiniti calls a "more sporting driving experience." If you want a manual in a car this size, it will probably have to be a BMW.
The other aspect of the M45 is its luxury package. My tester's black and silver interior featured sumptuous leather seating that offered heating and cooling settings. Thanks to the optional Sport Package ($1,650), they were deeply bolstered, too.
The Sport Package also bumps the wheels to 19-inchers, upgrades the steering wheel and shift knob leather, and puts aluminum on the pedals. Even more interesting, the package provides Rear Active Steer, which uses electric motors, connected to a series of sensors, to change the rear geometry of the suspension to enhance handling, making the big sedan especially light on its feet.
Speaking of technology, the optional Advanced Technology Package ($2,800) provides the Lane Departure Prevention (LDP) system. Some cars now will beep out a warning if they sense you're wandering into the next lane but this one actually gently activates the brakes on the side opposite the lane departure to gently nudge the car back from the white lines.
"More than 55 percent of fatal auto accidents in the United States are caused by lane departures, including single vehicle and head-on accidents," said Ben Poore, vice president, Business Unit. With the LDP system, the driver doesn't give up control, but the system still saves lives.
There's much to like about the M's other safety features. The Vehicle Dynamic Control and Traction Control System automatically adjust brake pressure and engine torque to help you control the car in slippery road conditions. Together with four-wheel power-assisted vented disc brakes with antilock, electronic brake force distribution, and brake assist, you're about as safe as you're ever going to be on wheels.
Besides the safety benefits, the Advanced Technology Package also features a stunning Bose 5.1 Studio Surround audio system with 14 speakers, including pairs mounted in the shoulders of each front seat.
Also, new for 2009, all M series cars get Scratch Shield self-healing clearcoat paint and automatic speed-sensing door locks.
In a fiercely competitive car market, what makes the M45 stand out? It looks completely modern, with an alert expression on its face, thanks to upwardly curved headlamp units on a smoothly integrated nose panel. The window greenhouse arches gracefully, and the wide taillamps push aggressively into the lower trunklid. It's nice, but doesn't stand out in the crowd.
Of course, all of the expected luxury features are standard, from high intensity xenon headlamps, rain-sensing windshield wipers and a power moonroof. Inside, you get driver seat memory, an intelligent keep-it-in-your-pocket key, dual-zone automatic temperature control, auto-dimming inside mirror and power windows, locks and mirrors.
Yet, despite all these things, the two-ton M45 doesn't quite match the cool style of the original Q45. Despite handsome detailing in Graphite, Stone or Wheat, the "Fine Vision" electroluminescent gauge package and an unusually shaped table-like center console, the M has all the parts but doesn't sing in its luxury performance role. And I'm not sure why.
M35 prices start at $45,800. My M45's sticker began at $52,150, but swelled to $60,765 with option packages and destination charges. For all-wheel drive, add $2,500 to the M45 and $2,150 to the M35.