The Infiniti M does not drive like a big car. Part of the reason is aluminum. The hood, trunk lid and doors are all aluminum, reducing the body's weight and helping lower its center of gravity. Also, the electrically controlled rack and pinion power steering is precise, with good road feel.

The M35 has one of the stronger V6 engines available, and it propels the M35 at a decent rate. The five-speed automatic transmission works well and shifts quickly. Drivers who want more control can use the manual mode, which works better than similar systems in some other cars, thanks to a short-throw shift lever more akin to that of a manual transmission in a sports car.

The M45 is a rocket, and it gives you the urge to floor the gas pedal just to feel the exhilarating acceleration from its V8 engine. Its EPA-estimated highway fuel mileage is only a couple of miles per gallon lower than with the V6. City mileage is the same.

The Sport Package includes what Infiniti calls Rear Active Steer. This system turns the rear wheels up to 1 degree, which isn't enough to be seen, but it helps turn the car into a corner more quickly and helps stop it from sliding out on exiting. Without trying two cars back to back it's difficult to determine how effective the rear-wheel steering is on the road. We haven't done that, but we have driven the Sport model and found it to be very stable, handling more like a good lightweight sports sedan in lane-change maneuvers.

Those who live in slushy, snowy climates should be wary of the Sport Package, however. These cars are equipped with sticky speed-rated tires, which are designed for lots of grip on dry pavement, and aren't much good in snow. Better to choose the all-wheel-drive M35x or M45x, which come with the same general-purpose, all-season tires as the base models. And with all-wheel-drive, the x-models add an element of confidence and security in sloppy climates, without a significant toll in fuel economy.

The M35x and M45x come with the same electronically managed ATTESA E-TS (Advanced Total Traction Engineering System for All Electronic Torque Split) all-wheel-drive system found in the G35x sedan and the FX35 crossover. We were less impressed with the overall effect of the M35x. The strength of the V6 engine is lots of power and torque, which in turn means good response and acceleration. Yet this is neither the most fuel efficient nor the smoothest V6 on the market, and that bit of not-so-luxurious coarseness seemed to be magnified in the M35x's all-wheel-drive powertrain, or at least in our test car. The AWD system itself is not as smooth or seamless as those in some other luxury cars, such as Audi's quattro system. During hard bursts of acceleration, the Infiniti's front wheels can generate a front-wheel-drive-style torque-steer effect, in which power from the engine twists the steering wheel in the driver's hands. Moreover, as power spreads out amongst the four wheels, it can create a driveline lash that comes across to the driver as a jerk somewhere in the bowels of the car. It adds up to a less-than-luxurious experience we haven't noticed in rear-drive Infiniti Ms. However, the M35x could still be a good choice for wet or snowy locales.

We haven't tried the new V8-powered M45x, but we have to wonder if its even more potent engine wouldn't exacerbate our complaints about the V6-powered M35x.

The RearView monitor, included in the navigation system, is impressive. It has a camera located in the back bumper that projects a view toward the rear onto the in-dash LCD whenever the driver shifts into Reverse. It's a great safety item as it can help a driver see objects or children behind the vehicle that are otherwise hidden from view. Infiniti's version goes one step further and displays a line on the screen that indicates the course of travel as the steering wheel is turned. It's a neat idea that works. Drivers still need to pay attention to ensure nothing is behind the car using traditional driving techniques, but rearview cameras provide the driver with useful information when backing up.

For 2008, the new Lane Departure Prevention system takes the concept of the previous system (called Lane Departure Warning) a step further by integrating with the VDC electronic stability control. Using a small camera behind the windshield to detect lane markings, the system warns the driver with a light and a buzzer when the car starts to wander into the next lane. If the driver does not voluntarily return the vehicle to the center of the travel lane, the LDP system gives the car a gentle nudge in that direction by lightly applying the brakes on one side of the car. LDP operates only above 45 mph, and is de-activated by the turn signals. The system monitors steering wheel movement to avoid false alarms when the driver intentionally changes lanes. An industry first, LDP makes its worldwide production debut on the 2008 Infiniti M, where it is included in the Advanced Technology and Premium Packages.

We haven't tried LDP, but we found the Lane Departure Warning system on the 2007 model valuable, especially when driving late at night on empty freeways or toll roads, although it was tricked once by stripes of tar on the road and thought we were straying from our appointed lane. This is a relatively new technology, however, so at this point there's no empirical evidence that such a system reduces accidents.

© 2008 NewCarTestDrive.com