MUNICH – I pull into the left lane of the autobahn a few miles north of the Austrian border and put my foot down at about 80 mph (120 km/h).

The U.S.-spec BMW 335d sedan makes a churning, mechanical roar and lunges forward like a runaway locomotive, quickly hurtling to the electronic speed limiter at about 135 mph (217 km/h). The cars in front scamper to the right lane like frightened animals.

Once I'm settled in the passing lane, the cabin quickly becomes hushed, with only a faint thrum emanating from the engine compartment. For a few glorious kilometers, I am the undisputed king of the road, loping down the autobahn at a ridiculous speed in the most fuel-efficient vehicle BMW AG ever has offered for sale in the U.S.

Maybe the auto industry's fuel economy binge won't be so boring after all.

More than 20 new diesel-powered cars and trucks will be introduced in the U.S. during the next two years, but if any vehicle can change America's mind about compression-ignition engines, this is the one.

Preliminary average U.S. Environmental Protection Agency numbers are 23/36 mpg (10/6.5 L/100 km). Yet the car accelerates to 60 mph (97 km/h) in six seconds flat, thanks to BMW's 3.0L twin-turbo inline 6-cyl. diesel that makes 265 hp and a pavement-wrinkling 425 lb.-ft. (576 Nm) of torque in U.S. dress.

The new selective catalyst reduction (SCR) emissions control system for the U.S. creates some backpressure that lowers output by 13 hp but does not affect torque.

The engine also is remarkably light, featuring an aluminium block. Most diesels have blocks made of much heavier cast iron or compacted graphite iron. Add iron to the robust design required for compression-ignition engines and you usually get a nose-heavy vehicle that corners like it has a snowplow hitched to the front bumper.

But because there is no big lump of cast iron sitting under the hood, the 335d has the same sharp reflexes as a gasoline-powered 3-Series. In fact, its nearly perfect 51/49 front-to-back weight-distribution ratio allows it to corner as well as any sport sedan on the road.

It is a little less entertaining to manually wind the 335d through the gears than its twin-turbo gasoline-powered sibling, but the additional 125 lb.-ft. (170 Nm) of torque creates its own special, more relaxed driving pleasure on challenging, twisty roads that would have you endlessly upshifting and downshifting with a gasoline engine.

BMW has been selling sporty diesels in Europe since 1983, and 71% of all BMWs currently sold in Europe are equipped with diesel powertrains, so it should come as no surprise the 335d is fast and fun to drive.

Aside from the inconvenience of having to hunt a little to find a diesel pump (in the U.S.), there are no compromises with this high-mileage car, especially when you can go almost 600 miles (967 km) between fillups.

Another benefit: It is likely that – unlike hybrid-electric vehicles – the 335d's real-world fuel-economy numbers will exceed the EPA's.

After about 180 miles (290 km) of flogging the car up mountain switchbacks and then blowing down the autobahn at 100 mph (160 km/h) or more, the trip computer reports average fuel consumption of nearly 28 mpg (8.4 L/100 km) and the 16 gallon (61 L) tank still is more than half full.

Diesel fuel prices now are coming down, edging closer to premium unleaded, which is the usual fuel for BMWs anyway, so the high cost of diesel fuel is not the issue it was a few months ago. And most fuel experts say diesel fuel prices should settle down in the U.S. for the foreseeable future.

In order to meet tough 50-state emissions requirements in the U.S., the 335d uses an SCR emissions control system it calls BluePerformance that neutralizes smog-causing oxides of nitrogen by injecting urea (labeled AdBlue) into the exhaust stream.

To introduce the SCR technology, which also will be required soon in Europe to meet upcoming Euro 6 standards, BMW has developed an active and passive 2-tank system that it says improves customer convenience.

’09 BMW 335d
Vehicle type front-engine, rear-wheel-drive, 5-passenger sedan
Engine 3.0L turbocharged I-6 diesel
Power (SAE net) 265 hp @ 4,220 rpm
Torque 425 lb.-ft (576 Nm) @ 1,750 rpm
Compression ratio 16.5:1
Transmission 6-speed automatic
Wheelbase 108.7 ins. (276 cm)
Overall length 178.8 ins. (454 cm)
Overall height 55.9 ins. (142 cm)
Curb weight 3,825 lbs. (1735 kg)
Base price (est.) low $40,000
Fuel economy 23/36 mpg (10/6.5 L/100/km)
Competition Lexus GS450 h
Pros Cons
Huge torque Fuel still expensive
36 mpg hwy Finding fuel not easy
Perfect weight balance Complex emissions control

Urea is injected from the active tank containing about 1.6 gallons (6 L) by means of a dosage pump.

The active tank and dosage pipes also are heated because the urea solution freezes at 12° F (-11° C).

The active tank is connected to a second passive tank that holds 4.5 gallons (17 L). Overall, engineers say a full load of urea adds about 50 lbs. (23 kg) to the vehicle's weight.

Having this much urea on board means the system only has to be replenished during regular oil change intervals, usually about every 13,000 miles (21,000 km).

Under normal circumstances, the customer will never have to bother with additional service, Wolfgang Mattes, BMW's head of U.S. diesel research and development says, adding the cost of refilling the tanks is covered under BMW's no-charge maintenance program for the first four years or 50,000 miles (80,000 km).

Mattes says the system will require early replenishment only under extremely aggressive driving. In that case, a warning light comes on about 1,500 miles (2,400 km) prior to the fluid running out.

If the driver ignores the warning, only about five starts will be allowed once the fluid gets within 200 miles (322 km) of running dry, Mattes says, but he emphasizes it is highly unlikely a typical BMW owner will ever face such a scenario.

Pricing will not be announced until closer to launch in December, but the 335d is expected to start in the low $40,000 range, including the $1,500 premium for the engine.

It also is eligible for an income-tax credit, but because it is based on EPA city fuel economy and vehicle inertia weight class, BMW officials cannot yet say how much the credit will amount to. They also will not comment on projected U.S. sales volume, except to say it is a “toe in the water.”

To be fair, there is at least one sporting hybrid-electric vehicle out there – the 340-hp Lexus GS450 h – that is capable of sparring a bit with the 335d as a car that also is green while fun to drive. But its fuel economy is an unimpressive 22/25 mpg (11/9L/100 km) and it is priced $10,000 more than the BMW.

Ultimately, despite all the hand-wringing over urea, diesel-fuel prices and other issues, diesel still offers a pretty sound value proposition.”Diesel always will be cheaper than hybrid technology,” Mattes says. It also likely will be more fun, too.

dwinter@wardsauto.com