Photos: 2008 Infiniti M45x

Infiniti, Nissan's premium brand, makes two sedans, the G and M series. The M is the larger, more expensive sedan, and is available as the M35 and the M45, the numbers signifying engine displacement. The M45x also has all-wheel-drive.

The M has some family resemblance to the G, notably in the raised front fender lines and the roofline. The M45x comes standard with adaptive front lights, which turn into corners.

The engine in the M45x is a 4.5-liter V-8 producing 325 horsepower and 336 foot-pounds of torque. It is not extraordinarily powerful, but it gets the job done. Our testing showed fuel economy of a little better than 16 mpg, about what you would expect from this engine.

The M has a longer back end than Infiniti's G sedan, and a more staid stance. Although the M45x has some performance characteristics, it seemed more suited to comfortable cruising.

The all-wheel-drive system in the M45x uses a system that distributes torque from 100 percent to the rear wheels to a 50-50 split between front and rear, depending on driving conditions.

The trunk is a little small to fit the luggage of the five passengers the cabin can carry comfortably.

Infiniti does an excellent job on the interior, with African Rosewood trim and incredibly comfortable seats. We were very happy to settle into this car for a long trip.

The steering wheel controls are nicely blended into the material, with audio controls on the left and cruise control on the right. There is also a button on the lower right to turn on Lane Departure Prevention, a unique system that nudges the car back into its lane if it starts drifting into another.

The adaptive cruise control is apparent from this view of the instrument cluster, where the speed is set at 72 mph, but the car is traveling a little under 60 mph.

We weren't impressed with the five-speed automatic transmission. It worked smoothly enough, but gear shifts felt typically slushy.

Next to the seat cooling and heating controls is a snow button. This reduces torque to keep the wheels from spinning in slippery conditions.

Infiniti's interface is very usable. The main knob has buttons inset on top that help navigate around screens. The LCD is also a touch screen, although it is a little far from the driver, and there is voice command.

Getting around this keypad to enter addresses is very easy with the multifunction knob, or you can lean forward and tap the letters on the screen.

The navigation system includes XM NavTraffic. The green line on one side of the freeway indicates free flowing traffic, while the amber line on the other side shows traffic traveling between 20 and 40 mph.

The stereo includes quite a few audio sources, including an iPod port and a DVD player.

iPod integration is excellent, letting you select artists and albums from the music library.

The Music Box feature is 9.3GB of hard drive space for storing music. If you put a standard CD in the car's disc player, you have the option to rip the CD to the Music Box.

As another digital music option, you can put music on a compact flash card and play it over the stereo.

The premium Bose sound system uses 14 speakers, including two shoulder speakers in each front seat, along with a subwoofer and a centerfill.

Bluetooth cell phone integration works very well. You can dial numbers with this keypad, or use voice command.

You can also upload your phone book to the car, although it requires a phone that can push phone book entries.