We'd likely never go so far as to declare any model "the perfect car." There are always going to be a few bones of contention, especially if price is a factor. But if we had to pick one car to wear the mantle of perfection, the 2009 BMW 5 Series would certainly be a nominee with good Vegas odds. It's a premium sedan (and wagon) with an arguably just-right size that looks good and is beautifully built. It's quiet and comfortable, yet handles better than just about anything else with four doors, and its engines are potent but utterly refined. In other words, if you have the money to spend, it's hard to pass up the 5 Series.

The 5 undergoes no major changes for 2009, although the iDrive electronics interface gets a slight overhaul as a midyear change. We strongly suggest waiting to get one of these cars. You'll be able to tell the difference between the two systems by the new design's menu buttons for frequently used functions (stereo, navigation, telephone) that are now adjacent to the control knob. Unfortunately, the same old menu structure remains -- unlike the 3 and 7 Series, which get the latest, greatly improved system.

Other than all-wheel-drive models getting "xDrive" attached to their name/number, the 5 Series range continues to consist of 528i, 535i and 550i for sedans and 535i xDrive for the wagon. Of all these, the 535i is certainly our pick of the litter. The primary reason is BMW's now-familiar twin-turbocharged inline-6, which endows the 535i with a near-ideal blend of seamless power and respectable fuel efficiency. This torque-rich engine pulls hard from low in its rev range, effortlessly piling on speed whether merging on the highway or embarrassing Camaro-wielding wannabe street racers. In fact, the 535i is just 0.4 second slower from zero to 60 mph than the V8-powered 550i, yet it returns only 1 combined mpg less than the 528i, which has 70 fewer horses. Additionally, this power plant weighs less than the 550i's V8, and that makes the 535i feel better balanced and more responsive in corners.

That being said, any 5 Series model would be a commendable choice in the midsize luxury sedan segment. It is certainly on the pricey side, and if getting more goodies per dollar is important, the Audi A6, Cadillac CTS, Infiniti M series and even the Hyundai Genesis are worth consideration. Meanwhile, for about the same price as the 5, there are the stylish Jaguar XF and the prestigious Mercedes-Benz E-Class to think about. However, none of these gets mentioned in the same sentence as "the perfect car" in their reviews. Although we'll probably never crown that particular champion, the stellar 2009 BMW 5 Series is one of the few cars that make us wonder if we should.

The 2009 BMW 5 Series is available in sedan and wagon body styles. Three engines are available on the sedan that correspond to the three trim levels (528i, 535i and 550i), with xDrive all-wheel drive available on the 528i and 535i sedans. The wagon comes in 535i xDrive trim only.

The 528i comes standard with 17-inch wheels, a sunroof, automatic headlights and wipers, power front seats with driver memory and power headrests, a power tilt-and-telescoping steering column, leatherette vinyl upholstery, automatic climate control, BMW Assist telematics, the iDrive electronics interface and a 10-speaker stereo with a CD player and an auxiliary input jack. The 535i adds adaptive xenon headlights and lumbar support and the 535i xDrive wagon adds a panoramic sunroof, fold-down rear seats and a power liftgate. The 550i adds parking assist, leather upholstery and auto-dimming mirrors.

Most of the features that are standard on upper-level 5 Series models are optional on the lower trim levels, as are numerous additional features. These include larger wheels, active steering, a lane-departure warning system, front and rear parking assist, an infrared night vision display, active cruise control, shift paddles for the automatic transmission, fold-down rear seats, rear sunshades, heated front and rear seats, a heated steering wheel (package only), multicontour power seats, keyless ignition/entry, a navigation system, a head-up display (which requires navigation), satellite radio, HD radio, an iPod interface and a 13-speaker Logic7 surround-sound audio system. The Sport package adds bigger wheels, a sport-tuned suspension, active roll stabilization, multicontour seats and a sport steering wheel. An aerodynamic body kit is included with the 550i's sport package, and on the M Sport Package available as a late model-year addition, which is otherwise identical to the regular Sport package.

BMW's model names and engine displacement used to correspond to each other, but not anymore. The 528i comes with a 3.0-liter inline-6 that produces 230 horsepower and 200 pound-feet of torque. The 535i gets a different 3.0-liter inline-6, this one twin-turbocharged to pump out 300 hp and 300 lb-ft of torque. The 550i gets a 4.8-liter V8 good for 360 hp and 360 lb-ft of torque. The sedans are rear-wheel drive by default, but the 528i and 535i sedans can be equipped with all-wheel drive. All three engines come standard with a six-speed manual; a six-speed automatic is optional.

Performance is adequate even in the base 528i, but for those who care about moving swiftly, an upgrade to at least the 535i is in order. We clocked a 535i with the manual transmission at 5.8 seconds from zero to 60 mph. The 550i is fleeter still, completing the same sprint in 5.4 seconds with the stick shift. Fuel economy is very good in the 528i (18 mpg city/27 mpg highway and 21 mpg combined with the automatic) and almost the same in the 535i sedan (17/26/20 mpg), with only a minimal penalty if xDrive is added. However, the 535i xDrive wagon drops to 16/24/19 with the automatic, and the 550 clocks in at 15/23/18 mpg.

Standard safety equipment includes stability control, antilock disc brakes, front-seat side airbags and front and rear side curtain airbags. Rear-seat side airbags are optional. The available lane-departure warning system alerts the driver via vibrations in the steering wheel if the car starts to veer out of its lane, and a night vision system warns of possible hazards out of regular headlight range. Both hill start assist and hill descent control are standard on AWD models.

In government crash tests, the 2009 BMW 5 Series earned only three out of five stars for driver protection in a frontal crash, although it did receive a full five stars for front passenger protection and front and rear side protection. In crash testing performed by the Insurance Institute for Highway Safety, the 5 Series achieved the top score of "Good" in the frontal-offset test. However, the IIHS gave it the second-lowest rating of "Marginal" for side safety because of potential torso injury risk for front occupants.

The 2009 BMW 5 Series is a well-balanced machine that can handle aggressive driving on winding back roads just as easily as it dispatches weekday commutes on crumbling expressways. The 5's adeptness at both ride comfort and handling prowess borders on the amazing. The steering is equally sublime, with perfect weighting and a near-telepathic feel. Opting for the sport package nets a sport-tuned suspension, bigger wheels and active roll stabilization, which enables the 5 to tackle tight corners as skillfully as some dedicated sports cars.

The 2009 5 Series boasts one of the most spacious and comfortable cabins in its class, particularly when optioned with the fantastic multicontour front seats, which adjust in seemingly infinite ways. Rear-seat head- and legroom are also satisfactory. In addition to the accommodating cabin, the 14-cubic-foot trunk can hold a fair amount of stuff, and its opening is wide. The wagon has a maximum cargo volume of more than 58 cubic feet.

The overall look of the interior is on the austere side, even though materials quality is beyond reproach. Early-year 5 Series feature the old iDrive electronics interface, which is needlessly complicated, particularly for ordinarily simple tasks like going from one stereo mode to another, and its display screen is responsible for the unsightly hump in the center of the dashboard. A midyear change adds a series of physical menu buttons that orbit the main control knob. This hastens access to those menus, but their submenus are still irritatingly laid out. The automatic transmission's joystick-like gear selector is also on the Rube Goldberg side -- an unnecessarily different and complex way of doing a fairly straightforward thing.