The perception of diesel vehicles has been changing for the better. Previously, it was thought that diesel vehicles were noisy, didn't offer much by way of performance, and were generally very dirty. Now, with improvements and new technology, diesels are much cleaner and provide quite the punch while returning excellent fuel economy. Of course, that doesn't mean everyone is convinced. To help change perceptions, Audi staged a TDI Efficiency Rally in Washington D.C. to highlight the benefits of diesels. Autobytel Road Test Editor, Dan Gray, was on hand to chronicle the event.