Audi is expanding its diesel offerings to include the 2014 A6, A7 and A8 sedans, and Q5 crossover, and the 2013 Q7. The new TDI models are powered by a new 3-liter V-6 engine, generating 240 horsepower and 406 pound-feet of torque. Fuel economy on the flagship A8 is estimated by Audi at 24 mpg city/36 highway, while the Q7 is estimated at 19 city/28 highway. The Q7 TDI has been available since September. The A8 TDI goes on sale next spring, followed by the A6, A7 and Q5 TDIs next fall.