Why Mess With Success?

For more than a decade, only two cars have really mattered to performance-minded buyers in the Ward's midsize luxury car segment: the BMW 5-Series and Mercedes E-Class.

With good reason. The German sedans have balanced executive-suite tranquility with world-class engines and chassis control for occasional dynamic driving.

Today, the E-Class is pummeling the 5-Series in sales, causing a bad case of Bavarian heartburn. The new E-Class sedan arrived last year about the same time BMW was building out the previous-generation 5-Series in preparation for this year's launch of the all-new 5.

But BMW AG executives are reasonably confident the '11 5-Series, going on sale this month in the U.S., will turn the tide on Mercedes, perfectly timed to capitalize on an improving economy.

The new sport sedan provides the proof necessary to support the argument.

Two new direct-injection gasoline engines (in the 535i and 550i) deliver more power as well as better fuel efficiency. Chassis dynamics are solid, considering a weight gain of about 400 lbs. (181 kg).

And new technologies include collision warning, adaptive cruise control, night vision and regenerative braking.

On the downside, the sixth-generation 5-Series doesn't look all that new. The car is bigger, but the overall shape basically is unchanged. Creases in the stamped aluminum hood, doors and front fenders add subtle flair, and shorter overhangs contribute to an athletic stance.

The interior could be mistaken for that of the 7-Series flagship, with which the new 5-Series shares architectural underpinnings and componentry.

There's nothing wrong with emulating the 7-Series. But it raises the question: Does a younger demographic for the 5-Series want something more sporty?

The plant in Dingolfing, Germany, produces both 7-Series and 5-Series.

Clearly, BMW was happy with the previous 5-Series and saw little need for a clean-sheet redesign. The sheet already was pretty clean to begin with. Why mess with success?

Without getting hung up on styling, BMW instead prefers to dazzle buyers with keen engineering and technology as building blocks for supreme drivability.

As with many BMWs, the most compelling story line is underhood.

The 550i adds the excellent 4.4L DOHC twin-turbo V-8 that also powers the 7-Series, 5-Series Gran Turismo and other BMWs. The “reverse-flow” engine delivers an extra 40 hp and 90 lb.-ft. (122 Nm) of torque when compared with the naturally aspirated 4.8L V-8 it replaces.

But the volume engine likely will be the 535i's turbocharged inline 6-cyl., which has been modified for maximum mileage.

This engine (codenamed N55) will seem very familiar to BMW aficionados, producing 300 hp and 300 lb.-ft. (407 Nm) of torque. That output is identical to the previous-generation N54 I-6, which used a more complex induction strategy requiring two separate turbochargers.

The N55 engine, instead, uses a twin-scroll unit in one housing, which allows the torque peak to arrive earlier, at 1,200 rpm.

With a fully variable third-generation Valvetronic throttleless intake, the new N55 earns the 535i a combined EPA rating of 23 mpg (10.2 L/100 km), 15% better than the N54 in the previous 5-Series.

A drive of the 535i confirms the EPA's mileage rating, despite spirited runs to the red line. Plentiful low-end grunt dismisses the concern that eliminating one of the turbochargers would result in turbo lag. Like the N54, the modified engine still sounds glorious.

The 535i and 550i go on sale in June, followed a month later by the 528i, which is powered by a naturally aspirated 240-hp I-6. All-wheel-drive versions also are on tap, and a diesel offering is expected as well.

Six-speed manual gearboxes are available in both the 535i and 550i, but the all-new 8-speed automatic gets better fuel economy with its taller cruising gears and delivers crisp shifting.

A new multi-link front suspension incorporates upper lateral A-arms (in place of the conventional struts) and double-pivot lower arms.

Similar to that of the 7-Series and X5, the mostly aluminum setup reduces friction, frees up space for larger brakes and delivers straight-line stability and excellent steering return coming out of curves.

The “Integral” rear suspension also is a multi-link arrangement.

Electric power steering appears for the first time in a BMW sedan in the U.S. Steering feel is natural and firm, without being over-assisted. BMW consistently represents the benchmark for steering feel, so consider the 5-Series application a coup for this emerging technology.

Pricing starts at $45,425 for the 528i, $50,475 for the 535i and $60,575 for the 550i. A sport package with 19-in. wheels adds $2,200; and a premium package with navigation, satellite radio, rear-view camera and premium audio adds $4,900.

Although the 5-Series makes up 20% of the brand's volume, it consistently generates 40% of the profits.