2009 Volkswagen Jetta TDI – Click above for high-res image gallery

The car as we know it is being redefined. Hybrids have reintroduced electrons to the driving experience, and the rumble, shake and shimmy of the internal combustion engine is being muffled and, in some cases, even silenced by cars like the Toyota Prius, 2011 Chevy Volt and Tesla Roadster.

For us to continue harnessing the energy of combustion under our hoods, we need to go much further on a gallon of fuel. Enter Volkswagen and the diesel-powered passenger cars it's been selling in the U.S. since the late '70s, the latest of which is the 2009 Jetta TDI. Follow the jump to find out how VW's newest diesel fares against the electrified future of the automobile.

Photos copyright ©2009 John Neff / Weblogs, Inc.

Most U.S. customers have largely ignored VW diesels. Early examples had their quirks, including an engine rattle that sounded like a Peterbilt and the propensity to puff out black smoke like a coal miner. Still, they could go twice as far on a tank of diesel compared to gas-powered cars and their engines lasted for hundreds of thousands of miles. A cult following has kept them going and many have been converted to run on vegetable oil and other bio-fuel blends.

It will be years before we know if the new 2.0-liter four-cylinder turbocharged diesel engine powering the Jetta TDI is as bulletproof as its predecessors, but we can tell you that its fuel efficiency is as impressive as ever. The EPA has rated the car at 30 miles-per-gallon in the city and 41 mpg on the highway. VW felt the EPA test cycle wasn't accurate and hired an independent company called AMCI to run more real world tests that yielded even better results: 38 mpg city/ 44 mpg highway.

We had the opportunity to take our TDI tester, which was *ahem* obviously provided by BOSCH, on a trip from Cleveland to Pittsburgh. We were specifically curious to find out if achieving similar highway fuel economy numbers as the EPA and AMCI required a hypermiler's touch, or if our lead-infused feet could manage equally respectable numbers. Long story short: Our best average fuel economy was 46.1 mpg on the highway.

The current fuel economy champ in the U.S. is the Toyota Prius, which the EPA rates at 48 mpg city/45 mpg highway. What makes the Jetta TDI so impressive is that it doesn't require a complex hybrid drivetrain to achieve similar results. The straightforward design of Rudolph Diesel's engine and an interstate, highway or autobahn is all that's required. In fact, the Jetta TDI doesn't even require a cross-country trip to show its stuff. Hop on the highway and within minutes the trip information display will report an average of 40+ mpg. Though high-speed cruising is when this powertrain is most efficient, we also achieved results in the mid to high 30-mpg range while running errands around town.

We didn't resort to drafting semis or cruising at insufferably slow speeds, either. Our average cruising speed was around 65 mph, and the only trick we pulled was shifting into Neutral down steep grades to keep some of the momentum that engine friction would have sapped away. The simple average mpg readout in the trip computer display was all it took to get us hooked on trying to improve our efficiency.

Most Americans have never driven a diesel-powered vehicle, let alone compared one with a gas-powered competitor. We have and can tell you that the experience of driving a diesel is markedly different. Aside from being less fuel efficient, gas-powered four-cylinder engines have to work much harder to keep you cruising. They're often described as loud and "buzzy" because highway speeds require most to turn over at a rate of 3,000 rpm or more.

Volkswagen's new 2.0-liter turbodiesel, which was named one of Ward's Auto's Top 10 Engines of 2009, runs at just 1,800 rpm while cruising between 65 and 70 mph, so the Jetta TDI feels and sounds more like a car powered by a large, unencumbered V6. It's relaxed and anything but buzzy, accomplishing all of its work below a 4,500 rpm redline that ensures things never get hectic underhood. Also gone is the knock, clatter and clang characteristic of past diesels. The Jetta TDI is as quiet as a luxury car on the highway, and though the diesel can be heard while idling, the entire car is eerily vibration free while sitting at a stop light.

The '09 model is also significantly quicker than VW diesels of the past, taking a tick above eight seconds to reach 60 mph, but even that metric doesn't tell the whole story. Though rated at only 140 horsepower, the engine's 236 lb-ft of torque means there's power aplenty. While off-the-line acceleration won't scare any sports cars, the Jetta TDI exhibits an effortless thrust when the right pedal is pushed. Whiplash inducing it's not, but the wave of power this little engine produces while underway is remarkable for its size.

Diesel engines have always been known their stump-pulling power, but they also have a reputation for being dirtier than gas engines. This became an issue a few years ago when California and the Environmental Protection Agency enacted their corresponding LEV II and Tier 2 Bin 5 emissions standards that erased the distinction between diesel- and gas-powered engines.

The modern diesel engine required major work to meet these new standards and gain access to markets in all 50 states, and most companies resorted to injecting a urea-based solution ahead of the catalytic converter that specifically targets the most harmful particulates like Nitrogen oxides (NOx). This solution, so to speak, was less than ideal because of the extra effort required to refill the solution at regular intervals. Volkswagen, in partnership with BOSCH, has developed a diesel engine for the Jetta TDI that's clean enough for sale in all 50 states without the use of a urea-based exhaust treatment system.

The trick is the use of a particulate filter in the exhaust system that requires zero maintenance from the driver. When the filter becomes full of harmful particulates, the engine's ECU will adjust the air/fuel ratio to raise exhaust temperatures high enough to burn them off. This process occurs every 300-500 miles and is all but transparent to the driver. Since raising exhaust temperatures requires a richer air/fuel ratio Fuel economy suffers slightly during this process, which we experienced on our way to Pittsburgh when we noticed a sudden but temporary 1.5-2 mpg drop in fuel economy.

The Jetta TDI isn't all about saving us from buying a few extra barrels of foreign oil. It also happens to be a dynamic small car with above average moves. The independent suspension with 16-inch alloys at all four corners exhibits typical German tightness with a solid ride that's not easily shaken. The standard, gas-powered Jetta has always been ahead of the economy car curve in this regard, and the TDI version is that much more so compared to cars like the Prius with its myopic focus on fuel efficiency at the expense of driving pleasure.

Another thing you're not going to get with a hybrid is transmission choices since most use a highly efficient CVT, or continuously variable transmission. Volkswagen offers two transmissions for the Jetta TDI: a good, old six-speed manual and six-speed DSG dual-clutch transmission with manual and Sport modes. Operating the row-your-own version is an above average experience for a small car, but the DSG is where you want to put your money. The latter will act like an everyday automatic if left to its own devices, but slip the stick over a notch and you're in control of precise shifts that occur quicker than you could make them yourself. VW deserves a double ding, however, for the lack of steering wheel-mounted paddle shifters and arranging the DSG's manual control as forward for up-shifts and backward for down-shifts.

There's still more decisions to make if you're considering the Jetta TDI, as VW also offers a SportWagen model in addition to the sedan. The four-door offers a 16-cubic-foot trunk, but the wagon goes above and beyond with 33 cu ft behind the rear seats and 67 when they're folded. While you may pay a small mpg penalty for the extra weight, the SportWagen TDI offers an unrivaled combination of utility and fuel efficiency in the marketplace. The EPA, however, reports the same results for SportWagen TDI as the Jetta TDI sedan: 30 mpg city/41 mpg highway.

For most, the decision to buy an exceptionally fuel efficient car like the Jetta TDI has less to do with making Mother Earth your BFF than saving money on fuel costs. The irony is that breaking the 40-mpg barrier adds a significant price premium to the up front cost of a car. In the case of the Jetta, the TDI version carries an MSRP of $22,270 versus the comparably equipped, gas-powered SE model that starts at $20,095. You may have noticed, however, that the Jetta TDI also qualifies for a $1,300 tax credit that more than halves the up front price premium, though that will only apply for the first 60,000 units VW sells.

Then there's the cost of diesel fuel to consider. When we topped of our tank, the price of diesel at our local station was $3.70/gallon versus $2.60/gallon for regular unleaded. Prices for both fuels have fallen since then, but the national average for diesel is still higher at $2.24/gallon versus $1.89/gallon. You will, however, go much farther on a tank full of diesel. Using EPA numbers, a Jetta TDI with 14.5 gallons of diesel could conservatively travel 595 miles on the highway before hitting empty, whereas our real world experience of over 46.1 mpg equates to 668 miles. A manual-equipped Jetta SE using a gas-powered 2.5-liter five-cylinder engine with 14.5 gallons of regular unleaded would stop on the highway after 450 miles.

The Jetta TDI has won us over because it offers what no hybrid on the market does: flexibility. Not only does it come in sedan or wagon form with your choice of transmission, but its mere existence represents an alternative for car shoppers who want fuel efficiency, but not at the expense of enjoying the car they drive.

Volkswagen will add to this equation by offering a TDI version of its Rabbit hatchback this fall using the same 2.0-liter TDI engine, and may also sell a street version of the Jetta TDI race cars that compete in the Jetta TDI Cup. There's also the Touareg V6 TDI on sale now and the Aud A3 TDI arriving later this year for those who need more utility or want extra luxury.

The 2009 Volkswagen Jetta TDI is a push back against our future of electrified motoring, and VW/Audi will soon be offering more diesel-powered models in the U.S. than ever before. A world that has silenced the sound of pistons pumping is not preordained, and the Jetta TDI proves that there is a way to meet stricter fuel economy standards without sapping the fun of driving from point A to point B with as many turns in between as possible.

Photos copyright ©2009 John Neff / Weblogs, Inc.

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