 The 2010 Prius has an estimated U.S. Environmental Protection Agency combined fuel economy cycle of .The Audi Duo III was introduced in 1997, based on the Audi B5 A4 Avant, and was the only Duo to ever make it into series production.The Duo III used the 1.9-litre Turbocharged Direct Injection (TDI) diesel engine, which was coupled with a electric motor.