Last week we started a series of the Five Best Used Green Cars To Buy.

We've already looked at two of the best-known green cars, the 2004-2009 Toyota Prius and the 2006-2011 Honda Civic Hybrid. Now it's the turn of a car known for its fuel, rather than its drivetrain--the Volkswagen Jetta TDI.

Where hybrids major on low emissions, the assistance of electric motors and high city MPG, diesels tackle fuel efficiency in a different way. Higher energy density of the fuel and more thermal efficiency in combustion means you can essentially do more, with less fuel. That means plenty of torque, and great economy--two reasons for the Jetta TDI's popularity.

History

Volkswagen has sold several generations of Jetta in the U.S, and TDI diesel models have become increasingly popular throughout that time.

While the Jetta TDI briefly disappeared from the market in 2007 and 2008 due to emissions regulations, a redesign for 2009 cleaned up its act and the model has been popular ever since.

The Jetta TDI uses a 2.0-liter turbodiesel four-cylinder, and puts 140 horsepower to the front wheels. More significantly, it also puts 236 pounds-feet of torque through the wheels--and it's this torque that TDI owners have come to love.

Driving experience, economy

2010 Volkswagen Jetta TDI Cup Street Edition

2010 Volkswagen Jetta TDI Cup Street Edition

It's probably fair to say that many hybrids ask you to sacrifice a little fun in your driving for the good of fuel efficiency--neither the Prius nor the Civic Hybrid we've covered so far are particularly fun to drive.

The Jetta TDI is different. With strong torque available from low revs thanks to the turbocharged diesel engine, it really punches through the gears, and even at freeway speeds it has plenty of shove for quick overtaking. It's also a lot more fun when you get to the corners, so even without considering economy the Jetta TDI has plenty of merits.

Also see: review of the 2012 Volkswagen Jetta / Used Volkswagen Jettas

When you aren't using all the available power, keeping the revs low to save fuel and relying on all that low-down torque means some impressive economy figures are possible--more than the EPA figures suggest.

While the manual Jetta TDI is rated 30 mpg city, 41 mpg highway by the EPA for an average of 34 mpg, many owners are achieving comfortably more--an average of 43.5 mpg, on the fueleconomy.gov site, based on 16 vehicles. Some owners are even getting as much as 52 mpg.

Unlike hybrids, which excel in the city, the Jetta TDI is at its best on the highway. Here, it's punchy, quiet--no traditional diesel "rattle" here--and very fuel-efficient indeed.

For fans of automatics, the Jetta TDI is also available with Volkswagen's excellent dual-clutch DSG transmission. It's slick, easy to use and adds 1 mpg to the car's highway rating.

2009 vw jetta tdi 009 1

2009 vw jetta tdi 009 1

Reliability, care

Like many vehicles, the Jetta TDI has been subject to a recall over the last few years. In this instance, all Volkswagen and Audi TDI models were recalled for a fuel leak issue. It applies to all Jetta TDI models built between May 2008 and September 2011.

The NHTSA also had to investigate a series of Volkswagen diesels stalling due to a fuel pump issue. The issue will now have been dealt with, but it's worth checking with your Volkswagen dealer to make sure the car you're viewing has had any necessary work carried out.

Otherwise, the Jetta TDI should prove fairly reliable. Volkswagen recommends servicing and oil changes every 10,000 miles, and changing it any earlier is really just a waste of money. These engines will do huge mileages--they're popular with taxi drivers in Europe, and it's not unknown for them to do hundreds of thousands of miles with only routine maintenance.

All Jetta TDIs will still be under their 12-year, unlimited mileage corrosion warranty, and some will still be under the five year, 60,000-mile drivetrain warranty.

2010 VW Jetta TDI DSG Automatic

2010 VW Jetta TDI DSG Automatic

Cost

For a 2009-2010 Jetta TDI, you can expect to pay between $20,000-$22,300 if buying a low-mileage car from a dealer, according to Kelley Blue Book.

Cars sold privately or at non-franchised dealers will cost less, and we found 2009 models on eBay from around $18,000.

If you go for an older Jetta TDI, before the model disappeared for a few years, you can spend much less--a 2006 model will cost you around $10,000-$11,000.

As far as fuel costs are concerned, you shouldn't pay too much. The EPA's fueleconomy.gov website estimates $1,800 a year in diesel over 15,000 miles, at an average diesel cost of $4.09 per gallon. However, with most owners achieving comfortably better MPG, you can expect to spend less than this for the equivalent mileage.

Our verdict

The Jetta TDI appeals to a different sort of buyer than the other green cars we've been covering in this series. It's more fun to drive for a start, which will immediately appeal to some buyers over others.

It won't match hybrids for fuel efficiency in the city, and really diesels aren't particularly suited to inner-city use--it takes longer for the engines to reach their most efficient operating temperature, where gasoline-electric hybrids can be fully up to speed in a matter of minutes.

However, if you regularly do longer highway journeys, a Jetta TDI is well worth considering. Highway economy is excellent--generally better than the EPA figures suggest--and you'll get to appreciate the torquey motor and strong performance.

You can also read a full review of the Jetta Sedan on our sister site, TheCarConnection.

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