Healey: Passat diesel is mpg marvel

Explain again, please, why a gas-electric hybrid is a good thing, worth the higher price and added complexity of two separate drivetrains.

Oh, yeah, that's right: mileage. Like 40 or 50 mpg, right?

So take note of the Volkswagen Passat diesel ("TDI" in VW-speak) because in real-world driving, the test car handily exceeded its government ratings of 30 mpg in town, 40 highway, 34 in mixed use, even though it was the victim of our lead-foot pounding.

Piloted less vigorously, it probably could deliver an honest 40 mpg in mixed use, 50 mpg highway, without resorting to sometimes unsafe hypermile driving tactics.

And it has a spacious interior. And, while not cheap, it is pretty reasonable. And it has elegant styling that probably will wear well on the eye. And it doesn't have a hybrid's big battery pack to cause you back-of-mind anxiety about reliability and replacement cost. And it's made in Chattanooga, Tenn., so more of your money stays home than if you buy a hybrid that's imported (as many are).

But, no. Passat TDI is a diesel, and we know from the sages in the auto industry that Americans don't buy diesel cars, so the story goes.

Except that 21% of Passat sales the first quarter this year have been diesels, VW says. In fact, 21% of all VW U.S. sales the first quarter � which includes models, such as the Tiguan SUV, that don't offer the diesel � were TDI models.

Not that the diesel Passat is flawless. On the test car, a couple of issues are noisily significant.

Our test car, a $29,000 Passat TDI with dry-clutch automatic gearbox (VW calls it a dual-shift gearbox), registered about 38 mpg in mixed use, 46 mpg on the highway before 20 miles of a stop-go traffic jam on the New Jersey Turnpike eroded that to 44 mpg.

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For awhile, it appeared the car would hold at 50 mpg, but herky-jerky traffic on I-95, even before that dreadful Jersey jam, began slicing the numbers back into the 40s.

As a Passat, the car is capacious in the way good ol' Detroit sedans used to be: stretch-out room, leg-flop space. Sized inside to allow you to lean, squirm, shift and stay alert and comfy on a long haul, though you might find you needn't move at all because the seats fit about right.

That upsizing was part of VW's Americanization of the car, which had been among the smaller, more-cramped midsize sedans.

On the plus side:

�The diesel engine starts quickly, runs quietly even when cold, generally intrudes not at all.

�The dashboard layout is attractive, and the big, simple gauges and fat buttons make life easy.

�Trunk is generous, closer to what you get on a full-size car than a midsize.

�Rear legroom and knee space are remarkable, more like full-size accommodations .

Gripes? Oh, yeah.

The worst two may be solved by now on newer-built models. The test car had significant wind noise around the driver's mirror, and a racket that sounded like the door banging in its opening when going over choppy bumps at highway speed.

VW blames the mirror for the noises, and says it has made running changes to quiet the airflow over the mirror and make it less likely to rattle over harsh bumps.

The lesser issues:

�Diesel fuel is more expensive, harder to find and smellier than gasoline. Diesel's been hovering around a nationwide average of $4.16 a gallon the past week, says AAA's FuelGaugeReport.com, and gas has been about $3.92.

�Radio's overly complicated; too many steps to do simple things.

�Backup camera's not available until next year. Meantime, rival Honda says it's putting the feature on 94% of its vehicles.

The government plans to require such cameras, but technical details have delayed the regulation.

�Despite the abundant low-speed torque that's a diesel's hallmark, Passat accelerates only modestly. A bigger-displacement diesel engine would be attractive (though at the cost of some mpg).

About the only time it matters, though, is trying to rocket forward to grab a hole in traffic or zip past a dawdler. You can do those things, just not as anxiety-free as you'd prefer.

In more-typical driving, TDI's power output is like frosting on a Cinnabon: sweet and abundant.

�The car "creeps" too aggressively in stop-go traffic. To improve mileage, the VW automatic lacks the fluid-filled torque converter (hence, "dry clutch") that allows a conventional automatic to ease ahead slowly, smoothly, gently in bad traffic, but burns extra fuel doing so.

Annoyances notwithstanding, Passat TDI is a very embraceable automobile.

�What? Diesel-power version of the Passat, a four-door, five-passenger, front-drive, midsize sedan. The car was redesigned for the 2012 model year.

�When? Diesel model, called TDI by VW, went on sale last September, same time as the gasoline-power version.

�Why? Diesels deliver high mpg, smooth power.

�How much? Base diesel with manual transmission starts at $26,765 including shipping, which is $2,270 more than similarly equipped gasoline version. TDI with automatic starts at $28,665.

�What makes it go? 2-liter, turbocharged, four-cylinder diesel rated 140 horsepower at 4,000 rpm, 236 pounds-feet of torque at 1,750 rpm. Available with six-speed manual or six-speed, dual-shift/dry-clutch automatic.

�How big? Same size as gasoline Passat, which is bigger than the previous version. Passat TDI is 191.6 inches long, 72.2 in. wide, 58.5 in. tall on a 110.4-in. wheelbase.

Weighs 3,393 lbs. (manual) or 3,459 lbs. (automatic), about 230 lbs. more than gasoline models. Passenger space, 102 cubic ft.; trunk, 15.9 cu. ft.

Turning circle, 36.4 ft., curb-to-curb.

�How thirsty? Manual transmission is rated 31 miles per gallon in town, 43 mpg on the highway, 35 in mixed driving. Automatic: 30/40/34.

Trip computer in automatic-transmission test car registered 38.1 mpg (2.62 gallons per 100 miles) in mix of city/suburban/highway driving, 46.3 mpg (2.16 gal./100 mi.) in brisk highway driving (dropping to 44.3 mpg after 20 miles of stop-and-go New Jersey Turnpike traffic jam).

�Overall: Honey of a cruiser, despite flaws.