For 2014, BMW offers diesel engines in its three sedan lines, and now we've spent a long weekend with the mid-size 5-Series sedan fitted with the fuel-efficient engine.

Given the depth-of-winter test schedule, its xDrive all-wheel-drive system was very welcome--and almost a necessity for our unpaved mountain driveway.

2014 BMW 535d xDrive, Catskill Mountains, Feb 2014

2014 BMW 535d xDrive, Catskill Mountains, Feb 2014

The 255-horsepower 3.0-liter turbocharged straight-six diesel is paired to BMW's new eight-speed automatic transmission, with the extra ratios letting it stay right in its most efficient output zone. It puts out a substantial 433 ft-lbs of torque, and moves the car along in appropriate BMW fashion.

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Over our usual test cycle plus a few errands, totaling 285 miles, we registered an impressive 35.6 miles per gallon (as displayed on the car's trip computer).

That's against an EPA combined rating of 30 mpg (26 mpg city, 37 mpg highway) and really shows how good modern diesels can be at highway speeds.

Our test route is roughly two-thirds highway miles, where diesels really excel, and one-third around-town stop-and-go urban and suburban traffic, where they're less advantageous.

Unlike other diesels we've driven, the 535d accelerated away from a stop with no appreciable lag in power, pulling steadily and accelerating swiftly enough to keep up with traffic and then some.

2014 BMW 535d xDrive fuel efficiency screen, weekend test drive, Feb 2014

2014 BMW 535d xDrive fuel efficiency screen, weekend test drive, Feb 2014

Despite temperatures in the low teens, it also started with no lag at all--again unlike a couple of other diesels we've driven in similar weather, which took a second or two before kicking to life.

The tone of the engine is quite different from gasoline 5-Series models: It's almost a heavy growl. BMW has obviously put a great deal of work into noise and vibration suppression, but the sound profile will be noticeable (at least to passengers who pay attention).

The latest BMW 5-Series is a handsome car, especially in the front with its beveled nose--more so than the previous series in our eyes--but not a particularly flashy one.

Our dark grey test sedan was fitted with the pricey M Sport kit, essentially a trim package consisting of sportier embellishments like fancy sill plates (and, to be fair, different 19-inch alloy wheels).

2014 BMW 535d xDrive, Catskill Mountains, Feb 2014

2014 BMW 535d xDrive, Catskill Mountains, Feb 2014

On the road, the 535d xDrive feels solid, even substantial, and the combination of all-wheel drive and traction control handled everything we threw at it.

While it's biased toward driving the rears, the road feel of all four wheels powering the car forward gives a different and more confident attitude when driving on roads that half-melted during the day and then froze solid again each night.

Behind the wheel, the steering lacks the feel of earlier generations of BMW--it's perfectly accurate, but numb. The optional "multi-contour" seats, however, were some of the best we've sat in. While we usually steer clear of $1,300 options, we'd go for these without hesitation.

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Our 2014 BMW 535d xDrive sedan carried a base price of $58,900. The charcoal paint--known as Dark Graphite Metallic--was an extra $550, although the black leather interior came standard.

2014 BMW 535d xDrive, Catskill Mountains, Feb 2014

2014 BMW 535d xDrive, Catskill Mountains, Feb 2014

The M Sport appearance kit was a notable $3,150, including 19-inch alloy wheels, aluminum interior trim, LED fog lights, an aero kit, a different steering wheel, and a few other bits and pieces.

Then there was the $1,900 lighting package (adaptive full LED lights and automatic high beams) and the $1,500 premium package (power trunk lid, keyless entry, and satellite radio). Added to that were a built-in universal garage-door opener ($500) and excellent multi-contour seats ($1,300), plus a mandatory $925 destination charge.

Overall, our fuel-efficient diesel BMW 5-Series sedan rolled out with a total sticker price of $68,725.

BMW includes four years or 50,000 miles of scheduled maintenance in the price.

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