The upside to fuel crises, if there must be one, is that carmakers offer up all kinds of solutions that would have no appeal in a low-cost and stable fuel marketplace. How else do you explain Cadillacs with V-8-6-4 engines? The downside, of course, is that once the perceived threat is over (or once we get used to $3-a-gallon gas) the market corrects itself, and these oddball crisis cars disappear as fast as they came. In some cases (i.e., the aforementioned Cadillac) that's a good thing; in others, the march of legitimate alt-fuel progress gets kneecapped. Thankfully there's Europe, where gas prices are reliably obscene.
It's been nearly a quarter of a century since BMW last offered American buyers a gasoline alternative — in the form of the 1985-'86 524td — and conditions are certainly right once again for a Bavarian-bred economy champ. And while we sat fat and happy in our Excursions, European diesel cars kept evolving — unlike that smoky, choky 524td, BMW's new diesel-powered 335d combines serious performance with remarkable fuel economy and serves them up in the ever-popular 3-series platform.
Indeed, the fact that the U.S. hasn't seen a BMW diesel in more than twenty years doesn't mean BMW hasn't been building them. In Europe, the company sells more diesel- than gas-powered cars, and it's gotten a solid reputation for building great oil burners. The heart of the 335d is a lightweight inline six-cylinder with intercooled, variable-nozzle twin turbochargers, common-rail fuel delivery, and high-pressure direct injection that borrows its basic architecture from the newest inline six gas engine used in the 335i. Like that engine, it employs such goodies as all-aluminum construction, electrically operated power steering, an electric water pump for reduced engine drag, and an alternator that engages only when the engine is off load.
Unlike its gas counterpart, which uses a pair of identical turbos — each fed by three cylinders — to boost output, the diesel version features a pair of asymmetrical chargers fed by all six cylinders. A small, low-inertia turbo comes on boost at low speeds for quick response and lots of torque from idle; as the revs build the exhaust gasses flow to a larger-capacity unit that allows for top-end power. The result is a very respectable 280 horsepower at 4000 rpm and a pavement-scalding 425 lb-ft of torque from 1750 to 2250 rpm.
The only transmission capable of handling that much torque is a GM-sourced six-speed automatic; the gear ratios are the same as the 335i's but the tranny features a taller final drive to take advantage of the massive torque spread. The combination allows the 335d sedan — the only model variant offered initially — to jump to 60 mph from a standstill in just 5.8 seconds. It's not just a sprinter, either, as it will gladly climb to its electronically limited terminal velocity of 155 mph, should you find the right stretch of Autobahn on which to try it. (Might we suggest European delivery?) Fuel economy is estimated at 23 mpg in city driving and 36 on the highway, figures that represent increases of 35 percent and 38 percent, respectively, over the 335i.
As fast and efficient as it is, the 335d also burns cleanly enough to be sold in all 50 states. While diesel engines generate less CO2 than gas motors thanks to their greater efficiency, the problem has always been the particulate matter, or soot, that comes as a by-product of diesel combustion. The 335d actually meets the EPA's Bin 5, Tier II emissions requirement, which holds diesel engines to the same standards as gas engines. It accomplishes this feat the same way many other new diesels do, through the use of a particulate trap and urea injection. The particulate trap, or catalyst, holds onto the sooty oxides of nitrogen that normally stream out of a diesel exhaust. A periodic injection of urea into the catalyst causes the oxides of nitrogen to reform as harmless ammonia, which then exits the tailpipe invisibly. Twenty-two liters of urea, enough for roughly 15,000 miles of driving, are stored in a separate tank at the rear of the car. The filler location is cleverly hidden behind a panel on the left side of the rear bumper, but chances are most owners will never have to refill the tank themselves since it's covered under BMW's extensive free maintenance program. Dealers simply top up the tank during scheduled service visits.
We picked up a U.S.-spec 335d in Munich and drove it to northern Italy and back, traveling sections of the German Autobahn as well as the serpentine mountain roads of the Austrian and Italian Alps. At startup and idle, the 335d is very obviously a diesel, with a signature clatter from under the hood. Let's just say you won't fool your neighbors when you back it out of the garage. The idle noise also permeates the cabin more noticeably than we expected, but disappears off idle. Once under load, the engine's audio track changes completely, sounding every bit like a conventional gas engine. The most unexpected surprise is the deep intake growl under full load, as when we were climbing switchbacks in the mountains. Where most modern oil burners have had their diesel burrs completely knocked off, the 335d seems to wear its engine as a badge of honor.
The first hard launch leaves no doubt about the factory's stated torque figure, with traction control working overtime to keep the 225/45-17 runflats gripping the road. Once underway, acceleration remains brisk at nearly any speed, despite a 5000-rpm redline. Overtaking slower traffic is predictably easy; there's only a momentary hesitation as the transmission downshifts to the right gear before the engine unleashes like a geyser. On the winding mountain roads, we kept it in third gear using the tranny's manual mode and rode the torque curve up and down the mountainside.
The weight penalty for choosing the diesel engine over the gasoline turbo — roughly 220 pounds — is split between the engine in the front and the urea tank in the rear, maintaining the kind of chassis balance for which BMW is known. All of the 335d's running gear is the same as the 335i's, so the driving experience is virtually identical. That means strong, responsive brakes and a nimble, sporty suspension tuned for mild understeer at the limits of tire adhesion.
When the 335d arrives in showrooms late this fall, it will have the same facelift all other 3-series sedans received for 2009. On the outside, this amounts to new bumper and light treatments at both ends, as well as a new hood design that adds more drama to the car's face. Inside, materials have been upgraded slightly in conjunction with new color combinations, and ergonomics have been improved with small touches, such as repositioned window switches. The big news inside, however, is the massively overhauled iDrive controller, which now includes a handful of main-function jump buttons as well as more intuitive menu structures — all of which improve the user-friendliness of that much-maligned multi-function interface.
Although pricing hasn't been announced yet, the diesel-powered 335d is expected to cost somewhere between $2500-$3000 more than a similarly equipped 335i, which puts the 335d squarely in the mid-$40,000 range. At that price, it's unlikely to attract penny pinchers looking to make the most of their $60 fill-ups. However, it does offer nearly identical performance to its powerful gasoline sibling with a substantial improvement in economy. With such a solid repertoire, the 335d should have an American-market shelf life longer than that of the average crisis-mobile.