THE strides made by Australian car manufacturers on improving efficiency of their large passenger sedans and wagons are no more evident than with the Calais Sportwagon 3.6 SIDI. With the benefit of direct injection and a decent boost in power and torque, the new 3.6 SIDI has lifted the Commodore six-cylinder engine out of aged mediocrity and into smooth modernity. Could this finally become the Holden six-cylinder that has a more rounded blend of performance, refinement and economy than the Commodore V8?