Predecessor of Audi A6 is Audi 100. The Audi A6 is available in both Avant and saloon body styles. It is by produced the German automaker Audi like an executive car.
 The second and third generation of Audi A6 was used as the basis for the "A6 allroad quattro" and "Audi allroad quattro" models respectively.
 All generations of the A6, were available as either with Audi's trademark Torsen-based quattro permanent four-wheel drive (4WD) system or front-wheel drive.
 There are 3 generations of Audi A6: C4 which was produced from 1994 till 1997, C5 - 1998 – 2004 and Audi A6 C6 which is produced from 2005 till present. It is related to Audi S6 and Audi RS6

Technical characteristics of the first and the third (last) generation of Audi A6

Audi A6 C4 (Typ 4A, 1994-1997)

 The latest generation (C4) of the Audi 100 was re-badged and facelifted as the Audi A6, to fit in with Audi's new alphanumeric nomenclature in 1994. The United Kingdom was the first market to receive the Audii A6, as stock of right-hand-drive Audi 100s had run out before expected, and before the rest of mainland Europe. The exterior was changed only slightly from the "C4" Audi 100 - new radiator grille, similarly with chassis, engine and transmission choices, and new front and back lights.
 Until 1997 the Ay was available with saloon and Avant bodies. The Auti A6 came with several different engines (such as 1.8 L Turbo I4, 2.4 L V6, 2.8 L V6, 1.9 L TDI I4 and 2.5 L TDI I5)  and most of them available with Audi's Torsen-based quattro permanent four-wheel drive system. Audi A66   C4 appeared with 5-speed manual, 6-speed manual and 4-speed automatic transmission. The dimensions are: wheelbase 2,760 mm (108.7 in), length 4,796 mm (188.8 in), width 1,810 mm (71.3 in) and height for Audi 6A  C4 saloon - 1,452 mm (57.2 in) and for Avant respectively 1,479 mm (58.2 in). Fuel capacity is 80 L (17.6 imp gal; 21.1 US gal).

Audi A6 C6 (Typ 4F, 2005-present)

 The new model (Audj A6 C6) is is longer (492 cm) but visually an evolution of the C5, features more sophisticated technology and incorporates the new Audi trademark "single-frame grille". Amazing is the Multi Media Interface (MMI) which is a system controlling in-car entertainment, climate control, car settings such as suspension configuration,  satellite navigation, and optional electronic accessories through a central screen interface.
 On the engine side, there was introduced the new Fuel Stratified Injection (FSI) direct injection technology. Now Audi AA6 (C6) appears with these engines: 2.0L Turbo I4, 2.4L V6, 2.8L FSI V6, 3.2L FSI V6, 4.2L V8, 2.0L TDI I4, 2.7L TDI V6, 3.0L TDI V6.  It has 6-speed manual, 6-speed tiptronic automatic or 7-speed multitronic CVT transmission. Its dimensions are: wheelbase - 2,843 mm (111.9 in) and for Audi A6 C6 LWB - 2,945 mm (115.9 in), length is 4,927 mm (194.0 in) and for LWB model - 5,035 mm (198.2 in), width - 1,855 mm (73.0 in). Height is different and divides in 3 types: for saloon is 1,459 mm (57.4 in), for Audi A6 C6 Avant - 1,463 mm (57.6 in) and for LWB model is 1,485 mm (58.5 in). Kerb weight differs from  1,520 kg (3,351.0 lb) - 1,845 kg (4,067.5 lb) and depends on the model. Fuel capacity for Audk A6 C6 is 80 L (17.6 imp gal; 21.1 US gal). 

The model was released in 2005 and its price varies from $21,600 to $75,900.