13/08/2008 09:01. Volkswagens 2009 Jetta TDI will run on new ultra-low sulfur diesel fuel, which is available nationwide in the U.S., and is an important factor as to why the new Jetta TDI is considered clean. Diesel fuel used to contain higher amounts of sulfur, which were harmful to emission-reduction devices like catalytic converters that are placed in the exhaust stream to clean up harmful emissions.

With ultra-low sulfur diesel, sulfur content was reduced by 97 percent. This allows automakers to add emission-reduction devices without the risk of damaging... // Cars.com