Audi engineers on camera admitted to some of the early TDI engines being "slow" but still valuable for their torque and, obviously, their fuel economy relative to gas-powered engines. A bunch of tinkering later, though, and Audi says its diesels can be a legitimate "part of a performance car" and has even overcome the issue of noisiness that's often associated with diesels.
The automaker made some news in these parts a few years back when its Audi A3 TDI won the 2010 Green Car of the Year at the annual LA Auto Show in late 2009, and the model even succeeded a fellow diesel (the Volkswagen Jetta TDI) to boot.
Granted, diesel sales aren't nearly as popular in the US as they are in Europe. Still, Audi last year boosted its diesel sales in the US by 40 percent to 10,076, which was about a tenth of what sister company Volkswagen sold in diesels last year in the States. And things have looked even rosier this year for Audi's TDI sales. Through June, Audi diesel sales have almost quadrupled from a year earlier to more than 8,100 units. Check out the 150-second video on Audi's 25-years of TDI production below.