FUEL-SAVING and emissions reducing technology is the new black in the automotive industry, with engine idle-stop the latest to be adapted widely by manufacturers. , , An addition to the Audi A4 range this year that boasts parsimony as one of its key attributes is the Audi A4 TDIe., , The A4 TDIe doesn’t just rely on a common-rail diesel and an engine on-off function, but also employs other fuel-saving tricks such as regenerative braking and tall gearing., , The question is, does the Audi live up to its green credentials?