If the idea of buying a $43,900 car to save money at the pump seems ridiculous to you, that's understandable, especially in today's economy. But before you pass judgment on those who disagree, answer these questions:

Is your shirt from Banana Republic, or Old Navy?

Did you purchase your sneakers at Puma, or Payless?

When we have the means, we tend to buy the nicest things we can afford, and it is the same with cars. That doesn't necessarily mean those who do are spendthrifts. In fact, one can make the argument that it is by not being wasteful that such people have acquired the bounty to buy a premium car in the first place, but that's for the President's task force to decide.

The BMW 335d will save its owners money - sometimes. The "d" indicates that it is diesel-powered, and the 3-liter twin-turbocharged 6-cylinder engine under the hood is rated at 23 mpg city and 36 mpg highway. That’s nearly 30 percent better highway mileage than a gasoline-powered 328i, and 40 percent more than the sportier 335i. After a massive spike last year, the price of diesel is currently below gasoline, so they’ll be counting a lot more change before they even start the car. At least for now.

Click here for PHOTOS of the 335d

Regardless of fuel costs, what the 335d conserves all the time is the fuel itself, which means less imported oil. More important to some buyers, it also emits less CO2, and has overall emissions that are 50-state legal, thanks to a urea solution that is mixed with the exhaust and causes a catalytic reaction to clean up the soot diesels are infamous for. Refills of the liquid are included in the 4 year/50,000 miles of free maintenance that comes with the car, and coincide with regular service intervals.

Of course, the 335d is first and foremost a BMW, the kind of automobile that people who are used to getting bonuses like to own, whether or not they are trying to be altruistic. Lucky for them it comes with a nice dividend of its own.

While the engine produces a reasonably healthy 265 horsepower, it also churns out an astounding 425 pound-feet of torque, the stuff that gives you a kick in the pants when you step on the gas. That's 30 pound-feet more than BMW's vaunted M5 sedan can muster, and one more than a Chevy Corvette has on tap. The result is that it is quicker than the 328i and can keep a 335i in its sights up to legal speed limits, and then some.

Once there, it trucks along nicely. The engine spins away lazily at low revs, which is part of the reason it gets better highway mileage than a 34 mpg MINI Cooper saddled with an automatic transmission, the only kind available on the 335d. Unlike most fuel sippers, press hard on the diesel pedal and after the briefest hesitation as the turbos spool up and the 6-speed finds the right gear, it's go time and you're waving bye bye to that gas-guzzling Lexus hybrid getting 25 mpg in the right lane.

Source of propulsion aside, the 335d is pure 3-series. It weighs about a passenger more than the 335i, but has the same nearly perfect weight distribution, and a sporty suspension that retains enough comfort for a cross country cruise, or a successful business lunch with the chairman of the board and his bad back.

If the urge to be irresponsible should strike you during the 580 or so miles you can go between fill ups, the 335d is able to rip a new one into your favorite road just as well as any of its fire-breathing BMW brethren. This combination of efficiency and performance is part of the reason why nearly 70% of the 3-series sold back home in Germany are of the diesel persuasion, far above the national average there of 53%.

For 2009 the entire 3-series lineup has been given a mild facelift inside and out. You'd be hard pressed to notice the exterior changes without a 2008 parked nearby, but there are a slightly modified grille and headlights up front, deeper rocker panels, and new taillights to compliment the reshaped rear bumper and trunk lid. Dual exhaust pipes on a diesel are a nice touch, and speak volumes about the personality of the 335d.

Alterations to the interior are also subtle. The overall look remains the same, but the materials have been upgraded and a few features have been shuffled around. The most obvious difference is that the climate controls are now located above the stereo, which may have something to do with the most notable change, a major overhaul of BMW's high-tech, but often infuriating iDrive multifunction interface and the functions it controls.

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A cluster of buttons have now sprouted around what used to be a lonely knob, giving you direct access to systems like navigation and audio without having to scroll through layers of on-screen menus. Even when you delve deeper into the features, the information is presented in a much simpler fashion on the enormous 8.8-inch monitor. Since BMW’s headquarters are in Bavaria, where the current Pope is from, it's not too much of a stretch to imagine the new 3-series pulling into a confessional and being absolved of the sins the old iDrive delivered unto humanity.

OK, that's actually a big stretch unless the car is named Herbie, in which case it would be a Volkswagen, making my scenario even more unlikely.

In any case, it should earn your forgiveness, as long as you're still in a spending mood. The basic infotainment system costs $2,100, and if you want to add satellite radio and an iPod/USB adapter to supplement the built-in 80GB hard drive, you’ll need to throw in another $995. Keep checking options boxes for other cool things that you can easily live without, like ultrasonic parking distance assist, and it's very easy to add $10,000 to the base price of the 335d. My test car checked out at $52,820, which brings us back to that part about being a spendthrift.

When all is said and done, a 335d will cost you about three grand more up front than a 335i with similar equipment. Generally speaking, you're getting the same car in a different flavor. Depending on what happens to the price of fuel you may end up with a lot more money at the end of your 5-year payment period, or a car that's worth a lot less when you go to trade it in, so it’s best to choose it because you like it, not because your calculator tells you to.

At least your carbon footprint will be smaller when you drive it to the mall to try on a new pair of Pumas.

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2009 BMW 335d

Base Price: $43,900

As Tested: $52,820

Type: front-engine, 4-door, 5-passenger sedan

Engine: 3.0L twin-turbocharged diesel inline-6

Power: 265 hp, 425 lb-ft torque

Transmission: 6-speed automatic

MPG: 23 city/36 hwy

What do you think of the 335d?

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