The Jetta has traditionally been Volkswagen's top seller in the U.S. and previous generations were little more than versions of the Golf two- and four-door hatchback sedans. That changed with Jetta's model-year 2011 redesign - although the SportWagen retained its Golf-heritage with new front sheetmetal to mimic the sedan's looks. The redesign dropped the Jetta's price, enlarged cabin space and sparked a sales increase that placed it fifth in the compact class for calendar year 2011, a position it has retained through the first half of 2012.

Volkswagen has a long history of integrating diesel engines into its lineup and is the leader in bringing modern, clean diesel technology to the U.S. The German automaker currently offers four clean diesel models with sales that total more than all of the other diesel offerings combined. The Jetta TDI (Turbocharged Direct Injection), sedan and SportWagen, is the leading seller, racking up more than 28,000 units through July.

For 2013, the Jetta TDI SportWagen has only minor changes over 2012 models; a leather-wrapped multi-function steering wheel and multi-function display on the S Trim.

Updates for the 2013 sedan TDI build on a series of changes VW began last year that include exterior styling tweaks and new interior appointments. On the outside, the sedan gains chrome grille accents and chrome window trim. Inside now includes power-recline driver and front passenger seats in addition to a leather-wrapped steering wheel, shift knob, and handbrake lever. A new iridium trim enhances the dash and door panels. Later in the model year, the TDI sedan will receive a soft-touch dash.

The top-of-the-line TDI Premium with Navigation trim now includes a six-way power driver seat and new 17-inch aluminum-alloy wheels that differentiates it from the 16-inch standard wheels of other models.

Pricing for the 2013 Jetta TDI sedan starts at $22,990, a $215 increase over the outgoing 2012 model. The SportWagen TDI has a sticker price starting at $25,540, the same as last year. EPA estimated fuel economy for both models is 30 city/42 highway and 34 combined.

Jetta TDI Sedan

The most significant change for the 2011 Jetta TDI sedan was that it received its own platform - it's no longer a Golf hatchback with a trunk added to the rear end. The car strains the definition of compact, pushing the envelope nearly into the mid-size arena. Its wheelbase grew 2.9 inches, to 104.4 and overall length is increased the same, to 182.2 inches.

By adding nearly three inches to the space that must be negotiated by hips, thighs, knees and toes, VW turned the backseat into adult-ready territory. And the trunk is large enough to handle more gear than any other sedan in the compact class.

The growth was accompanied by a new body-style that continues for the 2013 model year. Tossed was the distinctive wide mouth grille, replaced with a more determined and synchronous face. Rearward of the toned-down proboscis, the look is less Germanic, more generic. While the Jetta is not stirring or striking, it is clean with sharp lines that provide an overall appearance of understated sophistication. It's a look that outdistances its intended compact car competitors.

The exterior's contemporary look is carried inside the car, with a driver-focused instrument cluster and uncluttered center stack. When used, switchgear has that solid feeling expected in a German automobile. That said, the cabin is the first place where the bean counters' influence is noticed - the rich looking, soft-to-the-touch materials of the outgoing model were replaced by shiny, not-so-soft plastic. VW obviously is correcting that.

The inside isn't the only place where the accounting types had their way with the sixth-generation Jetta. The multi-link rear suspension was replaced with a less expensive torsion-beam design. Those who regularly check the engine's vital fluids will find the gas struts that hold up the hood are gone, ditto the trunk lid struts, replaced with gooseneck type hinges that intrude into the trunk space.

Jetta SportWagen TDI

The 2013 Jetta SportWagen TDI is basically the same vehicle it's been for several years, with an underbody structure of the 2005-2010 Jettas. Notwithstanding its own distinct styling, the SportWagen is easily identified as a Jetta family member. The cabin continues with high-quality materials that are noticeably better than the sedan.

Riding on a three-inch-shorter wheelbase, the SportWagen is smaller than the Jetta sedan resulting in a more constricted rear seat area than the sedan. But if you're buying a wagon you're looking for cargo room and the wagon boasts 32.8 cubic feet of cargo volume behind the rear seat and 66.9 cubic feet with its rear seat folded. That's comparable to many crossovers.

There's a new SportWagen in the works that should show up in fall 2013, and may or may not be named a Jetta SportWagon. It's expected that there will be shortages of the wagon around the end of the year so, if you like the current edition, buying sooner than later is advised.

For 2013 both the sedan and wagon are equipped standard with remote keyless entry; power windows, locks and outside mirrors; air conditioning; an AM/FM radio with CD player; adjustable front seats; and a tilt and telescopic steering wheel. Most of the usual options are available including a navigation system that includes the new Fender audio system with an SD card slot and iPod integration.

On The Road

Volkswagen provided a Jetta TDI sedan with a six-speed manual transmission for a weeklong evaluation. TDI is a direct injection system where fuel is sprayed directly into each cylinder, rather than into a pre-combustion chamber. A turbocharger and intercooler are also used. Together, these components result in cleaner emissions and better acceleration, the latter due to diesel's higher-torque characteristics. The 2.0-liter four-cylinder diesel furnishes 140 horsepower and a very healthy 236 pound-feet of torque.

We did three stints with our Jetta TDI to get a reading on fuel economy: We clocked 56 miles on city streets, 241 miles of mostly interstate driving and a fun-filled 137 miles on two-lane back county roads.

During our in-town driving trek I put on my "conservative" driving hat and forced myself to shift gears according to the up-shift arrow on the instrument cluster. Shifting into fourth gear at 30-32 mph, as the arrow directed, was difficult. But apparently the folks at Volkswagen know how one should drive to squeeze out fuel economy because I wrung out 33.8 mpg. (So much for the way EPA arrives at its numbers.)

The following day we topped off fuel two blocks away from Interstate-5 and headed south from Olympia, Washington to Portland, Oregon. On this leg we drove mostly in the right lane and limited speed to between 60 and 65 mph. On the return, far left lane driving seemed more like the natural place for the Jetta and we cruised most of the way at 75-80 mph. We exited where we started and pumped 5.63 gallons of diesel. That's 42.8 miles per gallon.

Three days later it was time for the turbo to spool up and stay there - and never mind the fuel mileage. There are some marvelous, seldom-used two-lane roads in the South Sound area of Washington State (Olympia/Tacoma). Blacktop surfaces range from silky smooth to almost gravel, with stretches of flat or hilly straight-aways and an abundance of blind corners and off-camber hairpin turns. For most of the 137 miles the transmission was in 3rd or 4th gear, making sure that the 30 to 50 mph posted speeds weren't exceeded by too much. The 236 pounds-feet of torque produced by 2.0-liter four arrives at 1,750 rpm, proving that you don't need a large displacement gas engine to have fun. And a 140 horsepower diesel validates that you can have a smile on your face while averaging 32.3 mpg.

The stretched wheelbase improves the Jetta's ride quality and despite the switch to a torsion-beam rear suspension, the sedan hasn't lost its taut, Teutonic feel on the road. Steering is tight, well weighted and communicative and the brakes are strong under foot and linear in their response. Cabin noise is at a minimum, even at highway speeds, with less road noise and wind whistle than expected for the class.

On The Green Side

On top of this, super-greenies and energy security hawks can run biodiesel in the Jetta TDI. The Volkswagen warranty only allows a 5 percent blend of biodiesel, but for some, rules are made to be broken - especially when considering the stakes of continuing our national dependence on oil. Biodiesel offers a 100 percent petroleum-free alternative today. (We can't tell you what to do; let your conscience be your guide.)

These opportunities are only possible because Volkswagen overcame the hurdle of California's Tier 2, Bin 5 emissions standards. Unlike the Mercedes Bluetec system, which injects urea into the exhaust system to convert NOx to nitrogen and water, the Jetta uses a NOx storage catalyst, which holds the emissions in a reservoir until they can be burned off by the engine. In addition, the common rail fuel injection uses piezoelectric fuel injectors, which permits higher injection pressure than a mechanical system. These clean diesel technologies, developed in partnership with Audi and Mercedes Benz, are a breakthrough in terms of neutralizing emissions and filtering out diesel-related particulates.

Exciting stuff, but when looking at overall low emissions, diesels still can't compete with hybrids. It's a big milestone for a diesel to pass California's Tier 2, Bin 5 standards, but that's still only about average for a new vehicle. Meanwhile, the squeakiest of squeaky-clean standards is the SULEV, reserved for the Toyota Prius, Honda Civic Hybrid, and a handful of other vehicles including the conventional version of the Volkswagen Jetta.

Diesel-makers will be quick to point out that the difference between Tier 2, Bin 5 and SULEV is negligible-considering that both of these standards are many times cleaner than past generations of cars and trucks. That argument is supported by the federal government's ruling the Jetta TDI is an "Advanced Lean Burn Technology Motor Vehicle."

Once upon a time, we all figured exceptional fuel efficiency would be the modern hair shirt-righteous but painful. With the 2013 Jetta TDI, Volkswagen has given lie to dire expectation and delivered a car that not only dispenses that exceptional fuel efficiency, it's actually a lot of fun to drive.