As a plan announced by Volkswagen, the Jetta TDI will return in the spring of 2008 as a diesel-powered vehicle and is expected to use the cleanest diesel in the U.S.

The 2008 Jetta TDI will be cleared for sale in all fifty states in the country.

Powered by a new 2.0-liter four-cylinder making 140 hp and 236 lb-ft of torque, the car can use either a six-speed manual or DSG automated manual transmission.

Some of the earlier introduced diesel-powered cars will only be available in 45 states. California, Maine, Massachusetts, New York, and Vermont have all adopted stricter emissions regulations for diesels that hinder the entry of some vehicles. Using advanced technology under the Blue Tec cooperative formed by Mercedes-Benz and Volkswagen, the Jetta TDI will not be affected by these stricter regulations, without resorting to a urea-based exhaust treatment, as many Blue Tec labeled models will.

Nitrogen oxides (NOx), along with particulate emissions (soot), are the biggest barriers facing diesels in the U.S. The task of most Blue Tec vehicles is to control NOx by injecting a urea-based solution called Ad Blue into the exhaust system upstream of a catalytic converter that specifically targets NOx. The ammonia in the urea in that catalytic converter reacts with the NOx in the exhaust gas and neutralizes it into nitrogen and water.

Volkswagen's Jetta TDI will be utilized without a urea injection system by using a NOx-storage catalyst. This catalyst is primarily a trap that temporarily holds the offensive emissions, just like the particulate filters in place on this car as well as on other diesel-powered cars. Periodically, the engine will switch to a richer air-fuel mixture. Eventually, it will create a hotter exhaust gas and burn off the material in the traps.

This new 2.0-liter common-rail diesel engine is up 40% horsepower over the previous 1.9-liter four-cylinder, with torque up 33%. These figures mean an average of 500% increase in drivability of the car. The additional power and torque produced by this new, cleaner engine bring that number down to somewhere in the low- to mid-eight second range. Under less aggressive feet, the TDI torque effortlessly prevents the Jetta away from stops and around traffic.

Along with particulates and NOx emissions, Blue Tec is rapidly abolishes that characteristic cylinder-full-of-pebbles diesel clatter as well. When the car is at a halt, the driver has to be paying very close attention to notice that the engine under hood is popping diesel fuel instead of gasoline. During acceleration, the exhaust sound is a little deeper and boomer than a gasoline Jetta. Nonetheless, driving experience becomes more relaxing due to the VW mufflers.

If you are not used to running a gasoline engine up to the redline, the only thing the Tri Delts will notice while driving the TDI is the inordinate number of leering stares they get at the diesel pumps.

Those are the good things about the Blue Tec. But despite the Blue Tec partnership, Volkswagen will refrain from using the name on the Jetta TDI. Reports say that consumers associate Blue Tec with Mercedes-Benz and wrongly assume that a Volkswagen with a Blue Tec badge is powered by a Mercedes engine.