The 2015 BMW 5 Series marks the fifth year of a somewhat controversial experiment. Before the current 5 Series debuted for 2011, BMW's midsize sedan was the benchmark for handling precision and driving satisfaction. But was that what customers really wanted? The company's product planners weren't convinced. So they tried a different tack this time, substituting size and comfort for cutting-edge athleticism -- and polarizing public opinion in the process.

Those who prophesied doom for the softer, friendlier 5 Series have, of course, been proven wrong, as the 5 Series continues to be a top draw for numerous reasons. You'll find a lot to like under the hood, from the 528i's overachieving turbocharged four-cylinder engine to the 550i's awesome twin-turbo V8 -- and don't forget about the 535i's accomplished turbocharged inline-6 and the 535d's ultra-efficient six-cylinder diesel. Meanwhile, the cabin is an expert show of restrained, finely wrought luxury, with an appealing array of up-to-date technology offerings. Really, the only thing missing is the rewarding handling of yore, but for many shoppers, the 5 Series' space and comfort will be more than adequate compensation.

Should you desire more sport in your sport sedan, a number of competitors have stepped up to fill the void. The 2015 Audi A6 feels notably lighter on its feet and competes well in the powertrain department, too. We're also fond of the impressively sporty Cadillac CTS and the polished 2015 Lexus GS 350. For a traditional luxury experience, the 2015 Mercedes-Benz E-Class beckons, while the Jaguar XF holds dark-horse appeal, making up for its dated interior with spirited performance and a distinctive character. But the 2015 5 Series remains an excellent all-around luxury sedan, and that's why it's still at the head of this hotly contested class.

The 2015 BMW 5 Series is a midsize luxury sedan available in four main trim levels that correspond to engine choice: 528i, 535i, 535d and 550i. Rear-wheel drive is standard, with "xDrive" all-wheel drive optional across the board. The ActiveHybrid 5 and high-performance M5 models are reviewed separately.

The base 528i starts with the four-cylinder engine, 17-inch wheels, adjustable drive settings (for steering, throttle and automatic transmission response), adaptive xenon headlights with LED accent lights, LED foglights, adaptive brake lights, automatic wipers, heated mirrors, a sunroof, cruise control and auto-dimming mirrors. Inside there's dual-zone automatic climate control, dark wood trim, ambient lighting, 10-way power front seats (with four-way power lumbar), driver memory functions, split-folding rear seats, leatherette premium vinyl upholstery and a power tilt-and-telescoping leather-wrapped steering wheel. Technology features include BMW Assist emergency communications, the iDrive electronics interface (with a 10.2-inch widescreen display and smartphone app integration), a navigation system, Bluetooth phone and audio connectivity, and a 10-speaker sound system with a CD player, HD radio, an auxiliary audio jack and a USB port.

The 535i adds a six-cylinder engine, 18-inch wheels and leather upholstery, but is otherwise similarly equipped.

The 535d is equipped exactly like the 535i, only with a diesel-powered six-cylinder engine.

The 550i upgrades to a V8 engine, a hands-free power trunk lid (opening or closing automatically when you pass your foot under the rear bumper), keyless entry and ignition, a sport version of the automatic transmission with steering-wheel-mounted shift paddles, front and rear parking sensors, a rearview camera and 20-way multicontour power front seats (with four-way power lumbar).

Engines aside, the standard features on the higher trims can be added to lower trims as options. Notably, the Premium package (528i, 535i and 535d) includes the hands-free power trunk lid, keyless entry and ignition, satellite radio and (for the 528i) leather upholstery. The 550i offers the Executive package, which adds soft-closing doors, ceramic-trimmed interior controls, a leather dashboard, a head-up display, an upgraded instrument cluster display and a 16-speaker Harman Kardon audio system with satellite radio. Most of the Executive package's contents can be added as individual options to lesser trims.

There are two major equipment lines available on 2015 BMW 5 Series models: Luxury and M Sport. The Luxury Line includes 18-inch (528i) or 19-inch wheels, upgraded leather upholstery and anthracite wood trim. The M Sport includes staggered-width 18-inch (528i) or 19-inch wheels, "shadowline" dark exterior trim (instead of the default chrome accents), an aerodynamic body kit, aluminum interior trim, a dark headliner and an M steering wheel. The Individual Composition package (not available on 528i) provides some of the same cosmetic upgrades as the M Sport package, adding different wheels and a faux-suede headliner.

Available across the board, the Cold Weather package provides retractable headlight washers, heated front and rear seats and a heated steering wheel, while the Lighting package features full LED adaptive headlights with automatic high-beam control. The Driver Assistance Plus package sets you up with a blind-spot warning system, a lane-departure warning system, side and top-view parking cameras and a forward collision mitigation system. The Dynamic Handling package, available on all models except the 528i, includes adaptive suspension dampers (with adjustable settings) and active stabilizer bars.

Stand-alone options include adaptive cruise control, an automated parallel-parking system (called Parking Assistant), an active steering system (featuring rear-wheel steering), an infrared night-vision display with pedestrian detection, four-zone automatic climate control, a Bang & Olufsen audio system, a power rear sunshade (with manual rear side-window sunshades) and a rear-seat entertainment system with twin tilt-adjustable 9.2-inch screens on the front seatbacks.

The 2015 BMW 528i is powered by a turbocharged 2.0-liter four-cylinder engine that produces 240 horsepower and 260 pound-feet of torque. An eight-speed automatic transmission is standard, and an automatic stop-start function shuts down the engine when the car stops in order to save fuel. In Edmunds performance testing, a 528i went from zero to 60 mph in 6.4 seconds, an average showing for a base-model midsize luxury sedan. EPA fuel economy ratings are 27 mpg combined (23 city/34 highway) with rear-wheel drive and 26 mpg combined (22/33) with xDrive all-wheel drive.

The 535i steps up to a turbocharged 3.0-liter inline-6 rated at 300 hp and 300 lb-ft of torque. Power is sent to the wheels through an eight-speed automatic transmission and automatic stop-start is standard. In Edmunds performance testing, a rear-drive 535i with the automatic went from zero to 60 mph in 5.9 seconds, another competitive result. Fuel economy for rear-drive models is 24 mpg combined (20 city/31 highway) with the AWD model getting 23 mpg combined (20/29).

The 535d features a turbocharged 3.0-liter diesel inline-6 that produces 255 hp and 413 lb-ft of torque. The eight-speed automatic and automatic stop-start are standard. In Edmunds performance testing, a rear-drive 535d went from zero to 60 mph in just 5.8 seconds. EPA-estimated fuel economy is an outstanding 30 mpg combined (26/38) with rear-wheel drive and 30 mpg combined (26/37) with xDrive.

Finally, the 550i boasts a twin-turbocharged 4.4-liter V8 that cranks out 445 hp and 480 lb-ft of torque. A sport version of the eight-speed automatic transmission is standard (it's optional on the other trims), as is auto stop-start. EPA ratings are 20 mpg combined (17/25) with rear-wheel drive and 19 mpg combined (16/25) with xDrive.

Standard safety equipment for the 2015 BMW 5 Series includes stability and traction control, antilock disc brakes, front-seat side airbags, side curtain airbags and active front head restraints. The braking system also periodically wipes the brake rotors dry in wet conditions and automatically snugs the brake pads to the rotors in preparation when you abruptly lift off the throttle. Moreover, the standard adaptive brake lights warn traffic behind you by getting brighter when you apply more brake force. Also standard is the BMW Assist emergency communications system, which includes automatic crash notification, an SOS button, remote door unlock and stolen vehicle recovery.

Parking sensors and a rearview camera are standard on the 550i and optional on other models via the Driver Assistance package (which also includes the head-up display and upgraded instrument cluster). A deluxe side and top-view parking camera system is available via the Driver Assistance Plus package, which additionally provides a blind-spot warning system, a lane-departure warning system and a forward collision mitigation system with automatic braking. Finally, the optional night vision system can identify potential hazards (including pedestrians) that are out of regular headlight range.

In Edmunds brake testing, various 5 Series models with optional summer run-flat tires came to a stop from 60 mph in distances ranging from 110-114 feet. Those are very good numbers, but they're pretty typical for sport sedans wearing summer tires. Most 5 Series models are equipped with all-season run-flat tires and will have slightly longer braking distances as a result.

In government crash testing, the 5 Series earned an overall rating of five out of five stars, with a four-star rating for frontal impacts and a five-star rating for side impacts. The independent Insurance Institute for Highway Safety gave the 5 Series its highest rating of "Good" in the moderate-overlap frontal-offset, side-impact and roof strength tests, while the 5 Series' seat/head restraint design was rated "Good" for whiplash protection in rear impacts. In the small-overlap frontal-offset test however, the 5 Series received the second-lowest rating of "Marginal".

If the 2015 BMW 5 Series were judged on its engines alone, few would question its "Ultimate Driving Machine" status. The 528i's turbo-4 punches well above its weight, and the six-cylinder 535i is a paradigm of smoothness. But the pick of the litter may well be the diesel-powered 535d, which is as fleet as the 535i and serves up 25 percent better fuel economy to boot. If you don't mind filling up more frequently, the 445-hp 550i throws down rocket-ship acceleration that's forceful enough to make an M5 fan think twice. Less appealing is the vibration you get when the auto stop-start system fires the engines back up from rest. Other automakers seemed to have figured out how to make their systems smoother.

We also don't like how the 5 Series never feels as nimble or precise as we'd like when going around turns, even with all the settings at their sportiest. The steering also lacks the precision for which it used to be renowned. So that's the bad news. The good news is that the 5 Series is blessed with a smooth, absorbent ride quality. If a luxurious day-to-day experience is more important to you than maximum performance, you're going to like how the 2015 5 Series operates.

The 5 Series cabin is attractive and trimmed with consistently high-quality materials, though it's not flashy. Elegant restraint is the name of the game here, and it's a game that BMW has played to perfection for decades. The instrument panel is a clear connection to the company's past with its classic twin analog gauges. Another heritage touch is the dashboard's understated center stack (the portion that includes the climate and audio controls), which cants toward the driver for a sportier, more intimate feel.

The central nervous system of every 5 Series is the iDrive interface, consisting of a high-resolution 10.2-inch display in the center of the dashboard and a rotary controller on the center console. The current version includes a touchpad on top of the controller that accepts "handwritten" finger inputs. It's pretty user-friendly, but some rival systems seem to require fewer presses or twirls of their controllers to get what you want.

The base front seats are comfortable in their own right, but the available 20-way multicontour seats just might be the best in the business, providing an incredible range of adjustments and sublime support for all driving scenarios. Rear outboard passengers will find satisfactory space in all directions, even if they're 6-footers, and the rear seats themselves are thoughtfully contoured and padded. Trunk space is relatively limited, however, measuring 14 cubic feet.