A BMW 5 Series sedan in Los Angeles is about as common as a publicly intoxicated David Hasselhoff — therein lies the appeal of driving the 2006 BMW 550i. It doesn't draw the attention of the typical performance car, let alone that of an inebriated Knight Rider.

Short of scrutinizing the silver badge on its trunk, the average suburbanite would never suspect that this Bavarian shares the same 4.8-liter 360-horsepower and 360 pound-feet V8 as its big brother the 7 Series. This is an additional 0.4 liters, 35 hp and 30 lb-ft of torque over the 4.4 liter it replaces.

New engine, new name, the 545i becomes the 550i, but the car's personality remains the same. A drive in the 550i is an experience of quality, satisfaction and exclusivity, like that hole-in-the-wall restaurant you stumbled upon and now can't get enough of. Just order light or the amount of the check might shock you.

New on the menu
The all-aluminum, double-overhead-cam 4.8-liter V8 borrows from M-sedan technology in the form of double VANOS (VAriable NOckenwellen Steuerung, a.k.a. variable valve timing). Both intake and exhaust valve timing adjust continuously based upon gas-pedal position and engine speed. The result is a torque band like a rainbow. Where does it end? This engine is as smooth and comfortable on winding canyon roads as on the highway.

At low rpm, the engine is silent. Like the little boy ordering an ice cream cone, staring in awe and anticipation of what's to come. As the needle tickles 4500 rpm, the driver can't help but giggle in a brain-freeze, chocolate-all-over-the-face appreciation of the guttural resonance now spilling from the 550i's otherwise unassuming tailpipe. It's cool.

Meat and potatoes
Acceleration testing was seamless and consistent thanks to the remarkable relationship between the car's clutch and its standard six-speed manual transmission. The quarter-mile fell in 13.8 seconds at 102.5 mph and a 0-60-mph time of 5.6 seconds was easily repeatable. Undoubtedly quick, but still two-tenths slower than BMW's claimed 5.4 seconds and the comparably priced 382-hp Mercedes-Benz E550 we tested the same day.

BMW says the optional Sequential Manual Gearbox (SMG) transmission (no extra charge) is claimed to parallel the acceleration numbers of the manual, while the Steptronic automatic (also no extra charge) is just one-tenth slower.

Equipped with the optional $2,300 sport package, our tester welcomed us with its lowered suspension, hip-hugging front seats, active roll stabilization and Bridgestone Potenza RE050A run-flat tires: P245/40R18 up front, P275/35R18 in the rear. Unlike many automakers offering run-flats, the 550i also offers a space-saver spare tire — hidden inside its enormous trunk. With such low-profile tires, the spare is a nice option to avoid the risk of damaging costly rims.

BMW keeps the rear-wheel-drive 550i lean by taking advantage of lightweight materials. Aluminum is integrated throughout the vehicle, including the engine, front-end structure and skin and suspension components. Less weight equals a faster car, and the BMW's 67.5-mph slalom speed spanked the Mercedes-Benz E550 (63.5 mph) and the all-wheel-drive Audi A6 S-Line (65.3) also tested that same afternoon.

When it came time to hit the brakes, the 3941-pound BMW also spanked its heavier German rivals. Stopping from 60 mph was an incredible 109 feet for the 550i, compared to the E550's distance of 126 feet and the Audi's 120 feet. Largely the result of its brake fade compensation system, the BMW's stopping distances grew progressively shorter until its ventilated discs and aluminum calipers logged their best distance on the fifth attempt. The 550i's pedal remained rock solid and consistent.

Appetizers
Agility and luxury have long been the key ingredients of a BMW. The 550i portrays the role of luxury as significant, but certainly not the main course. This philosophy is reinforced by the scope of cosmetic updates for '06, which are limited to refined leather surfaces and refinished control knobs. The interior is otherwise cosmetically unchanged and continues to offer a choice of Premium, Premium Sound, Cold Weather and Sport option packages.

The cabin remains spacious, with room for a party of five and ample space in the backseat for long-leggers. In contrast, there is a notable lack of room for cell phones and other sundries. The center console appears to offer usable storage space, but further inspection reveals a compartment-within-compartment design along the lines of a Russian Matryoshka doll.

Brussels sprouts
Despite the efforts and intentions of the chef, there's always something that doesn't appeal to a diner's taste buds, and the 550i is not exempt from this rule.

BMW diehards questioned the exterior styling of the new 5 Series since its makeover two years ago, and the debate still rages. If you didn't like the update back then, we have bad news for you because nothing's changed for '06.

That's not the worst of it — iDrive remains standard equipment on the 550i. It takes an experienced user up to six steps just to change the radio station. Is "not user-friendly" the polite way to say this sucks, or is "non-intuitive" better?

Our test car also had the standard push-button start positioned on the dash, which still requires that the key fob be stuffed into the steering column before starting the car. We did not have the Comfort Access option, which (for a grand) activates the push-button start remotely and removes the key-in-ignition step. Don't overlook this feature.

Check, please
Optional features such as head-up display, navigation system and the aforementioned sport package raise the cost of this 5 Series quickly from its $57,400 base price. Tack on the gas-guzzler fee of $1,300 and the bottom line is a pricey sleeper that tempts the palate for $65,090.

Expensive for sure, but the 550i delivers enough levels of luxury and performance. High enough to leave its competition in the rückspiegel and high enough to justify the amount of the check.