The "M," as it's called by INFINITI, is now available in four different models; there's the V6-powered M35 and the V8-powered M45, both of which can now be had with either rear-wheel drive or all-wheel drive. The 4.5L, DOHC V8 makes 325 horsepower in the M45, while the M35 now comes with an updated 303-horespower version of the 3.5-liter V6 originally delivered in the second generation G35 sedan. The V8 is especially noteworthy; it has titanium valves, a microfinished crankshaft, lightweight pistons and a single-stage cam drive-chain for quiet-running and robust power delivery. Both engines come with a 5-speed automatic transmission that includes a manual shift mode that automatically matches revs during downshifts for a sporty feel and better control. An independent double-wishbone suspension design in front and multi-link setup in back, along with stabilizer bars, helps handling. The doors, hood, and trunklid are made of aluminum for weight savings while also improving handling. The all-wheel-drive system that's now offered with either engine reverts to a 50/50 distribution for standing starts and limited-traction situations, then it delivers up to 100 percent up to the rear wheels when cruising or when needed for traction. Electronic stability control is also included, with standard anti-lock brakes with electronic brakeforce distribution and brake assist. A newly available lane departure prevention system, which makes its worldwide debut on the M and INFINITI's EX35 SUV, uses a small camera to detect when you're drifting out of your lane and applies slight brake pressure to the wheels opposite the drift to gently guide the vehicle back into position. Even though it's equally a sport sedan, the M's interior is equipped in the style of the best luxury cars, with leather upholstery matched with rosewood or aluminum trim. Standard leather seating and climate-controlled front seats are also included, plus a very long list of luxury conveniences. The available Sport Package, in addition to appearance enhancements inside and out and larger 19-inch wheels and tires, includes the rear active steer system, which uses electric motors to precisely adjust the rear-suspension geometry for better control depending on steering input and vehicle speed. INFINITI claims that the system helps bring sports-car-like agility with luxury sedan stability and ride quality. Standout options include a Bluetooth hands-free phone system, a rearview monitor, intelligent cruise control, and heated power reclining seats in back. The top available sound system employs Bose surround sound and has 14 speakers, including two speakers mounted onto the shoulder area of each front seat.