There are few cars that achieve such a perfect mix of comfort and fun like the 2008 BMW 5 Series. It is a wolf in a flamboyant sheep's clothing: a comfortable midsize sedan that handles and performs like a sports car. And for a real surprise, a wagon model offers the same wolf but in utilitarian pack mule clothing. While other carmakers relentlessly pursue this automotive pinnacle, BMW consistently raises the bar to keep itself on top of the heap.

For 2008, the current-generation BMW 5 Series receives its most important update since the car's 2004 introduction. Most significantly, there are two new six-cylinder engines in the 5's lineup. Last year's 215-hp 525i model has been replaced by the 230-hp 528i. Even more significant is the mid-level 2008 535i. Replacing the 530i, the 535i comes with an all-new 300-hp, twin-turbo engine. Along with the V8-powered 550i, the new engine lineup makes the 5 Series an even more attractive performance sedan.

With new, innovative technologies coming at a mile-a-minute pace in this premium midsize luxury segment, BMW has introduced several standard and optional features for the 2008 5 Series. Six-cylinder models now offer Brake Energy Regeneration, which takes a page from hybrid powertrains by capturing excess braking energy and using it to power the car's many electronic systems.

There's also an upgraded cruise control system this year. Optional on automatic-transmission 5 Series, Active Cruise Control with Stop & Go works much like Mercedes-Benz's Distronic Plus by maintaining vehicle distance at highways speeds and in stop-and-go traffic. For safety, a new Lane Departure Warning system option alerts the driver through vibrations in the steering wheel when the car starts to drift out of its lane.

The 2008 BMW 5 Series remains one of our favorite midsize luxury cars, even if its endless technology can seem a tad reminiscent of HAL 9000. Its deep options list can also raise the 5's price tag into the ionosphere, with the 550i easily reaching $70,000. Nevertheless, for those with deep enough pockets, the 5 Series offers a level of driver involvement unmatched by its competitors.

The 2008 BMW 5 Series is available in sedan and wagon body styles. There are three engines available on the sedan, which boils down to three individual rear-wheel-drive models: 528i, 535i and 550i. The 528xi and 535xi sedans come with all-wheel drive. The wagon is only available as a 535xi.

The 528i and 528xi come standard with 17-inch wheels, a sunroof, power front seats, leatherette upholstery, automatic headlights and wipers, automatic climate control, BMW Assist telematics and iDrive control interface. The 535i and 535xi add xenon headlamps and lumbar support, while the 535xi wagon adds a panoramic sunroof, fold-down rear seats and a power tailgate. The 550i throws in 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-level models.

The options list is exceptionally long on the 5 Series and it got even longer for 2008. High-tech features include Active Cruise Control with Stop & Go, a lane-departure warning system, active steering, a head-up display, infrared night vision, keyless ignition, high-definition radio, the next generation of iPod integration and a navigation system with updated iDrive and real-time traffic. Other options include ventilated front seats, heated rear seats and rear side airbags. A Cold Weather package adds heated front seats, heated steering wheel and retractable headlight jets. A Sport Package on rear-wheel-drive models includes 18- or 19-inch wheels, a sport-tuned suspension, active roll stabilization, a sport steering wheel and multicontour seats.

The BMW 5 Series' engine lineup is more powerful than ever, but more confusing with model names that no longer correspond with engine displacement. The 528i comes equipped with a naturally aspirated 3.0-liter inline-6 that produces 230 hp and 200 pound-feet of torque. The 535i has BMW's impressive new twin-turbocharged, 3.0-liter inline-6, capable of 300 hp and 300 lb-ft of torque. The 550i is the lone power plant to carry over untouched, still pumping out its ample 360 hp and 360 lb-ft of torque. This engine motivates the 550i from zero to 60 mph in 5.6 seconds.

All three engines come standard with a six-speed manual, while a six-speed automatic is a no-cost option. This is good news for consumers since most 5 Series are sold with the autobox. In summer 2007, a new Sport automatic transmission with paddle shifters will be optional on Sport Package-equipped 535i and 550i sedans, replacing the previous car's SMG gearbox. BMW's xDrive all-wheel-drive system is optional on the two six-cylinder sedans (they become 528xi and 535xi), and standard on the 535xi wagon.

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 and, due to safety concerns, you must specifically request that your dealer activate the bags if you order this option. A new optional lane departure system alerts the driver via a shaking steering wheel if the car starts to veer out of its lane, while a night vision system illuminates possible hazards out of regular headlight range. Both Hill-Start Assist and Hill Descent Control are standard on AWD models, in case your extra-steep driveway ever gets slippery. In IIHS testing, the 2008 BMW 5 Series earned a top score of "Good" for its protection of occupants in frontal-offset crashes. In side-impact tests, however, the 5 Series earned a disappointing score of "Marginal," the IIHS' second-worst score.

The 2008 BMW 5 Series is an extremely balanced machine that can handle aggressive driving maneuvers on winding back roads as well as it dispatches weekday commutes on crumbling expressways. The optional active steering system hasn't dulled BMW's trademark steering feel, though driving purists will prefer the standard setup. Likewise, the standard suspension tuning gives the 5 Series plenty of capability in the corners. The new six-cylinder engines shared with the 3 Series offer more power than the outgoing units, especially the 300-hp 535i that exhibits virtually no turbo lag. Equipping the 5 Series with the V8 turns it into a seriously fast sedan that will outpace many sports cars.

Although the interior looks unchanged, there were a few key updates made. The window switches have been relocated to lower on the driver door and on Steptronic automatic-transmission models, an electronic gear selector like the one found in the X5 now resides on the center console. It's certainly interesting looking, but this odd little gizmo is largely an unnecessarily different and complex way of doing a fairly straightforward thing.

The same can be said of iDrive, the mouse and LCD screen control system standard on all 5 Series, even those without a navigation system. It now has six programmable memory buttons that can control everything from a radio preset to a frequently traveled destination. Slow and steady progress perhaps, but iDrive is still as user-friendly as a shift knob made of razor wire. Build quality and materials inside the 5 Series are still outstanding, although competitors offer more stylish and less austere environments. Supportive seating is provided in both the front and rear, and even adults won't mind sitting in the commodious backseat. The sedan has 14 cubic feet of trunk capacity, while the wagon has a 34-cubic-foot cargo bay behind its fold-down rear seats, along with standard roof rails.