The 2003 M45 was based on the Y34-series Nissan Gloria/Nissan Cedric, with styling similar to the Gloria. The engine is Nissan's 340 hp VK45DE V8 which produces 333 ft.lbf of torque. The rather Japanese squared-off styling did not make much of a splash on the US market, and the M45 sold poorly.
Infiniti released a completely redesigned M for the 2006 model year to compete directly in the mid-size sport luxury class, against such class stalwarts as the BMW 5-Series and the Mercedes-Benz E-Class. It uses a much more rigid version of the G35/350Z/FX Nissan FM platform and is available with the common VQ-series 280 hp (208 kW) 3.5 L V6 in the M35, or the Q45's 335 hp (249 kW) 4.5 L V8 in the M45.
The automotive press has awarded the M several best-in-class awards in direct comparisons against its competitors. Despite entering a very crowded, competitive segment in which almost every member has been recently redesigned, the M still managed to find many key distinctions: Both the M35 and M45 are fastest in their class (0-60 in 6.3 and 5.4 seconds, respectively). The M is near or at the top of every interior dimension, actually breaking into the EPA "large" category depending on which option packages are selected. In fact, while being smaller on the outside than the flagship Q45, the M45 boasts more room, greater performance, a superior multilink front suspension, and much friendlier ergonomics, threatening the position of the flagship Q45.
All-wheel-drive models are called the M35x, which uses a sports car derived system (ATTESA-ETS) to send all power to the rear wheels until slip is detected.
The M line was released in February 2005 (at almost exactly the same time as the new 2006 Lexus GS) and its first several months of sales have been far beyond expectations. Prices in the US (USD) range from approximately 40,000 - 55,000, which feature for feature tend towards the lowest in class