The A4 has gone through five generations of modifications and is based on the Volkswagen Group B platform. The automaker's internal numbering considers the A4 as a continuation of the Audi 80 line - the initial A4 is designated the B5 series, followed by the B6, B7, B8 and B9. The B8 and B9 series are built on the Volkswagen Group MLB platform, shared by many other Audi models.
The A4 body is produced as a sedan and station wagon. The second (B6) and third (B7) generations of the A4 had a convertible body, but then from the fourth generation (B8) it became a separate model called the Audi A5. There is a sports version of the A4 called the Audi S4.
Development of the car began in 1988 and the first design sketches were created at the end of that year. By 1991, the exterior design was chosen and frozen until production in 1994. The interior design was completed in 1992 and experimental production began in the first half of 1994. Development was completed in the third quarter of 1994.
The car's closest competitors are BMW 3 Series, Volkswagen Passat, Kia Optima, Infiniti G, Honda Accord, Hyundai Sonata, Opel Insignia, Peugeot 408, Ford Mondeo, Mazda 6, Mitsubishi Galant, Mercedes C-Class, Nissan Teana, Renault Laguna, Toyota Camry, Subaru Legacy and Skoda Superb.
Audi B5 (1994-2001)
The first generation of Audi A4 (Typ 8D) debuted in October 1994, production began in November 1994, and European sales began in January 1995. Sales in North America began later in September 1995. The car is built on the Volkswagen Group B5 (PL45) platform, which is based on Volkswagen Passat fifth generation. Two body types were produced - a 4-door sedan and a 5-door station wagon (Avant).
During the seven-year production, minor changes were constantly made to the car. A significant reconstruction was carried out in 1997. Some engines were updated and a 6-speed manual transmission was added. Another facelift was made in 1999. The changes were mainly cosmetic, but affected almost all external elements.
The choice of engines is very large. Petrol 4-cylinder with a volume of 1.6 to 1.8 liters and a power of 101 to 180 hp, 6-cylinder V-shaped with a volume of 2.4 to 2.8 liters and a power of 150 to 381 hp. Diesel 4-cylinder with a volume of 1.9 liters and a power of 75 to 115 hp, 6-cylinder V-shaped 2.5-liter engine with a power of 150 hp.

Audi B6 (2000-2006)
Next Audi A4 (Typ 8E) debuted on October 10, 2000, now based on the Volkswagen Group B6 (PL46) platform. The car's new styling was developed under the direction of German car designer Peter Schreyer between 1996 and 1998, inspired by the design for the second generation Audi A6 (C5), introduced in 1997.
The body came in three variants - a 4-door sedan, a 5-door station wagon and a 2-door convertible. The Avant (station wagon) was introduced in June 2001 and arrived in European showrooms in September 2001.
A choice of engines for the most demanding tastes. Petrol - 4-cylinder with a volume of 1.6 to 2.0 liters and a power of 101 to 187 hp, 6-cylinder V-shaped with a volume of 2.4 liters (168 hp) and 3.0 liters (217 hp). Diesel - with a volume of 1.9 liters (l4, 99-128 hp) and 2.5 liters (V6, 153-178).

Audi B7 (2004-2008)
Audi introduced the new generation of the A4 in late 2004 with the internal designation B7 (Typ 8E/8H). The car is built on the Volkswagen Group B7 (PL46) platform. Despite the new designation, the B7 is a heavily modernized and updated version of the B6, with revised steering settings, suspension geometry, updated combustion engines, and an improved electronic stability program (ESP). The front grille assembly has changed to a high trapezoidal shape similar to that of the third-generation Audi A6 (C6), but the dashboard and interior are largely unchanged.
The body also came in three versions: a 4-door sedan, a 5-door station wagon and a 2-door convertible.
A number of engines have received many additions. In 2005, the fuel injection system (FSI) was introduced for the 2.0 TFSI and 3.2 V6 FSI petrol engines, as well as other improvements, which increased the power to 197 hp and 252 hp, respectively. These engines use a four-valve-per-cylinder configuration.

There are four transmissions to choose from: a 5- or 6-speed manual, a 6-speed automatic "Tiptronic", and a continuously variable transmission "Multitronic" (CVT) with a choice of seven speeds.
Audi B8 (2009-2015)
Audi presented the first official photos of the A4 B8 series in August 2007 and showed the car to the public at the Frankfurt Motor Show in September 2007. The car is built on the Volkswagen Group B8 modular longitudinal platform (MLB/MLP), a platform that is also used for the Audi A5 coupe. Cars with a convertible body became known as the Audi A5, and only two body styles remained to choose from - a 4-door sedan and a 5-door station wagon.
The MLP platform allows for a shorter front overhang, resulting in a longer wheelbase without increasing overall length. This effectively redistributes the centre of gravity slightly rearwards, improving handling and vehicle mass balance between the front and rear axles. The new platform also increases cabin and luggage space, while the vehicle's kerb weight has been reduced by 10%.

There are five different transmission options available - a 6-speed manual, a 6-speed "Tiptronic", an 8-speed automatic, a 7-speed DSG "S tronic", and an "8-speed" CVT "Multitronic".
Audi B9 (2015-present)
In June 2015, the next-generation Audi A4 B9 (Typ 8W) was released - the fifth model to bear the A4 name and the ninth generation of the Audi 80/A4 series overall. The official launch took place at the Frankfurt Motor Show in September 2015. The car is built on the Volkswagen Group B9 (MLB/MLP) platform. The B9 is slightly larger in size than the previous generation, but weighs 120 kilograms less. There are also two body styles to choose from - a 4-door sedan and a 5-door station wagon.

There are three transmission options to choose from: 6-speed manual or 7- and 9-speed DSG "S tronic".












