Among the 2009 BMW 3-Series changes are (slightly) revised styling, an upgraded interior, simpler iDrive interface, in-car Internet access, a new audio system, and an optional dual-clutch transmission. The automaker's sublime 3.0-liter inline-six, available in both naturally aspirated and twin-turbo form, remains the same, but for the first time BMW is also giving Americans the option of a diesel powertrain -- and it could turn out to be the best of the bunch.

Along with the carryover engines, the 2009 BMW 3 Series sedan and wagon continue to feature a standard six-speed manual and optional automatic, but now buyers of the 335i coupe or convertible can opt for BMW's new seven-speed, dual-clutch DCT transmission as well. Offering lightning-fast shifts and no loss in traction, the DCT helps the 335i post better performance numbers than its 2008 cousin.

American buyers looking for some relief at the pump will get the chance to try out one of BMW's lauded diesels. For 2009, the automaker is finally offering an oil-burning option in the form of the 335d. A 3.0L twin-turbodiesel inline-six featuring common-rail direct injection, the mill puts out approximately 286 hp and a stunning 428 lb-ft of torque, while reaching 62 mph in a respectable 6.0 sec -- just 0.4 sec behind the topline BMW 335i. Yet despite this, according to BMW the 335d averages 35 mpg, which is 9 mpg better than the twin-turbo gas model, and 7 more than a slower, naturally aspirated 328i.

Key changes to the 2009 BMW 3 Series include a new hood with dual character lines leading down to a broader, chrome-ringed double kidney grille. There are new bumpers front and rear, new exterior rearview mirrors, plus new headlights and taillights. The front track has been increased 6 mm, while the rear has been pumped out 24 mm. Six new wheel designs are available. Inside the 2009 BMW 3-Series are mild upgrades to the interior, including a smattering of classier new materials, revised instrument graphics, and the latest-generation iDrive system, featuring the new controller and button cluster from the just-released BMW 7 Series and the same glitzy, high-resolution graphic interface. The 328i and 335i drivetrains continue unchanged for 2009, but they are joined by BMW's first 50-state-legal diesel, a twin-turbo, 3.0L straight-six that delivers 265 hp at 4220 rpm, and a thumping 425 lb-ft of torque between 1750 and 2250 rpm. Driving through a six-speed automatic transmission, BMW claims this engine will propel the 335d from 0 to 60 mph in 6.0 sec while delivering 23 mpg city and 36 mpg on the highway.

I still find BMW's sport suspension a bit too aggressive in regards to the rebound setting on the dampers, but the 2009 BMW 3-series still is the best driving car in the class. The rest of the segment just doesn't offer the communicative steering and wonderful chassis balance of the 3-Series.

As for the power? I've never driven a 330i, but the 328i does lack the oomph of the 335i. That said, the BMW 128i is fun because it forces you to make good use of the gearbox, and it's the same case here, though the 3-Series' added heft does dog the I-6 a bit more.

The first thing I noticed when climbing into this updated 2009 BMW 3-series was the new iDrive interface. Wow, is it ever impressive. It is very intuitive and has very impressive graphics. I instantly felt at home juggling through the various menus.

The next thing you notice, of course, is the torque of the 2009 3-Series' twin-turbo diesel engine. In the cold and wet conditions of winter, the traction/stability control is working overtime keeping the rear tires in check. It's a good thing BMW has a good, smooth stability control system. The 335d is fast and the rest of the car is typical of a BMW. It has a slightly choppy ride on rough Michigan roads but it seems to be better than our Four Seasons 330i was, when I compare both on 17-inch wheels. This is no doubt helped by the fact that this 335d lacks the optional sport package. The steering is still lovely and most of the controls are intuitive and feel robust.

I would happily give up some of the 335d's torque and fuel economy for the 335i, which is cheaper and less expensive to fill up (and purchase). Add in the fact that the gasoline engine sounds better, has more horsepower, and is offered with a manual transmission, and I'm going to have to say no to Dr. Diesel's sales pitch in this case.

Just like the 335i, the newest 2009 BMW 3-series uses a 3.0-liter, aluminum-block in-line six with piezo direct injection and two turbochargers. The 335d is available exclusively with a six-speed automatic-none of the manual transmissions in BMW's arsenal can cope with the diesel's massive 425 lb-ft of torque.

There's an overlay of diesel clatter below about 2500 rpm, but because BMW has remained faithful to the balanced in-line six engine layout, none of it translates to harshness. No, from just off idle to its redline, this diesel engine is damn near as smooth, rewarding, and quick as its gasoline counterpart. In fact, the only place where the BMW 335i feels quicker is in the first few feet off the line. Despite using one teensy turbocharger and one larger one to diminish lag (in place of the 335i's identical twin turbos), the 2009 BMW 335d is a bit hesitant to get going from a stop. Once moving, though, the engine's computers perform a constant dance, routing intake and exhaust gases to either (or both) of the turbos to minimize lag and maximize output.