Many years and generations ago, the 528i was the turbine-smooth, six-cylinder pinnacle of the 5 Series range. This engine capacity first appeared late in the life of the original 5 Series in 1979, last appeared two generations ago and reemerges today as the entry model of the current 5 Series lineup. But not as a 2.8-liter, nor even a six-cylinder.
The 2012 BMW 528i engine is now a 2.0-liter turbocharged four-cylinder. The mill even looks downsized when you open the hood, a sizable void yawning between the nose of the engine and its radiator, yet it generates a promising 240 horsepower — identical to that of the outgoing 2011 six-cylinder 528i, but boasting an extra 30 pound-feet of torque. And, thankfully, 0.4-second-quicker sprint to 62 mph (6.3 seconds).
Economy and emissions gains are the main goal of the displacement and cylinder reduction. The 2012 528i improves on the 2011 model's fuel economy by 1 mpg city and 2 mpg highway and achieves an EPA rating of 23 city/34 highway mpg. The improvement is aided by a new stop-start system integrated into the standard eight-speed automatic transmission. But the key to this new engine's fuel-sipping strength is a single twin-scroll turbocharger that functions in concert with a number of well-established BMW technologies.
These include double VANOS variable valve timing and the company's Valvetronic induction system, which does away with the throttle plate. The 528i's four-cylinder routes exhaust gases from each pair of cylinders to a separate turbine inlet to speed the engine's reaction to a twitching right foot. Fuel is fed by precisely metered, solenoid-controlled direct injectors, while refinements to the Valvetronic system have also improved its precision.
Torque From Low Revs
The result is a very impressive 240 hp from 2.0 liters and even more usefully, a stout 258 lb-ft of torque from as low as 1,250 rpm. This torque stream is sustained all the way to 4,800 rpm, promising the kind of midrange punch that normally aspirated six-cylinder gas engines rarely offer. And you can feel its effects almost as soon as you move off, the 2012 BMW 528i advancing with a confident authority that's heightened by the tremor-free activities of its eight-speed automatic transmission.
All those ratios help disguise the steep ramp to the torque peak, which kicks in with authority as the revs approach 2,000 rpm. But to uncover this, you must switch to manual shifting so you can hold the car in a gear, trickle it down to 1,000 rpm in 2nd and stomp on the accelerator as if you hate it. There's a brief pause, followed by an excitingly exponential surge that leaves no doubt that this is a rapid car. By 2,000 rpm it's pulling like a lashed mule and there's a substantial power spike at 3,500 rpm. The acceleration is unrelenting until 6,500 rpm, when the transmission automatically upshifts to let you do it all over again.
Though this four has lost the turbinelike wail of the six, it's more powerful and it stays smoothly unfussed until it closes on 6,600 rpm. The culture of the six is gone, but there's more honest muscle to this engine. Those familiar with a BMW straight-6's smooth-spinning ways will miss it some, but it makes the 5 Series a better car. There's some refinement missing, but the return of lighter fuel bills, more torque and extra entertainment is a worthy trade.
Control Your Driving Experience
Further entertainment can be had from the new rocker switch occupying the center console near your right knee. Grandly labelled the "Driving Experience Control," it alters the throttle response, steering weight, stability control thresholds, transmission shift strategy and the calibration of the dynamic dampers, which come with both the M Sport and Sport option packages.
There are four settings, labelled "Sport+," "Sport," "Comfort" and "Eco Pro." Driving Experience Control is most worthwhile if you ordered those dynamic dampers, whose settings alter the character of the car noticeably from the pillowy comfort of a big, old Buick — though without the wallow — to sensations distinctly more athletic when you aim the 528 at a bend and hard-charge it. As you'd hope of a car promoted as a sport sedan, it spears them with a satisfyingly quiet confidence that's sharpened by the fact that the four-cylinder engine in its nose is lighter than the outgoing six.
Select the Sport+ mode, which relaxes the stability control system's interventionist policy and you can indulge the occasional tail slide. But it's the smooth and rapid fluency down the road that characterizes this car more so than exploring the outer reaches of its rear tires' grip. The 528i's dynamic capabilities can now be further stretched with four-wheel drive, as the xDrive option's rear-axle-biased torque distribution largely preserves the 5's rear-drive character.
High Tech, Low Consumption
And Eco Pro? It's about fuel economy strategies for both you and the car. The car's contribution is to lower the energy demands of the air-conditioning and assorted electrical systems such as the heated front seats, while providing you with some fuel-saving driving guidance. This includes an infotainment display whose bar graphs track the car's consumption over the previous 15 minutes while providing a rolling average. That's good, but the occasional appearance of rather obvious driving tips, such as "accelerate moderately" will irritate some drivers.
The 2012 BMW 528i is a car with an unusual breadth of personality, ranging from comfortable econo-sedan to sporting four-door. And this efficient new twin-turbo four allows it to pull off these character switches with conviction. Yet it's not a car of split personality. The satisfying way in which it gels makes it easy to understand why this is the best-selling sedan in its class, worldwide.
Edmunds attended a manufacturer-sponsored press event to facilitate this report.