The Environmental Protection Agency (EPA) has expanded the scope of their Volkswagen diesel investigation to the company's 3.0 V6 TDI engines. In the US, the V6 TDI is fitted to the Touareg, Audi A6, A7, A8, Q5, Q7 and diesel powered Porsche Cayennes and Macans.

Volkswagen Auto Group's V6 TDI is the company's premium diesel engine. First introduced in 2002, the premium diesel option first saw service in the second generation Audi A8. The V6 TDI is available in various power outputs, ranging from 204 to 320 PS.

EPA officials will be scrutinizing the V6 TDI equipped cars to see if those also have the “defeat devices” seen in the 2.0 TDI models. Cars equipped with the 2.0 TDI engines include the Volkswagen Beetle, Golf, Jetta, Passat and the Audi A3. The EPA has issued Volkswagen and Audi a stop-sale order for 2015 and 2016 TDI cars until the German car maker fixes the cars. Despite not being covered by EPA, Volkswagen has also halted TDI sales in Canada. Canadian authorities have also launched their own investigation regarding Volkswagen diesels.

Volkswagen has admitted that the “defeat device” has been fitted in 11 million four cylinder TDI powered cars worldwide. The 2.0 TDI is one of the most popular engine options for Volkswagen Auto Group products, commonly seen in Volkswagens, Audis, SEATs and Skodas in Europe. While sales of the 2.0 TDI have been halted, the V6 TDI is still available in the US with the cars mentioned above.