Below is a list of light bulb types used in 2004-2011 AUDI A6 lighting system, covering estate and saloon 4-door vehicles.
Headlight bulb: low beam - H7, D2S or D3S / high beam - H1, H15, D2S, D3S or H7
Parking light bulb: W5W
Fog light bulb: H7 or H11
Front indicator/turn signal bulb: PY21W
Side direction indicator bulb: WY5W
Daytime running light bulb: H15 or P21W
Cornering light bulb: H8
Rear indicator/turn signal bulb: PY21W or P21W
Tail light bulb: P21W
Brake light bulb: P21W
Back-up light bulb: P21W or W16W
Rear fog light bulb: H21W or P21W
License plate light bulb: C5W
Interior light bulb: C10W or C5W
Door light bulb: W5W
Boot light bulb: W5W
Entry light bulb: W5W
Reading light bulb: T4W or T5W
Glove compartment light bulb: W5W
Light bulb sizes for other AUDI A6 generations: A6 (C4) / A6 (C5) / A6 (C7)