The 2017 Audi S8 uses integrated LED lighting for both the low-beam and high-beam headlights. The supplied fitment data does not list a separate halogen, HID, projector, or non-projector headlight option, so no headlight bulb code is specified.
Other exterior lighting is also listed as LED, including the fog lights, front and rear turn signals, daytime running lights, cornering lights, parking lights, side markers, tail lights, brake lights, center stop light, reverse lights, license plate light, and door-mirror lights. These assemblies may require an LED unit or assembly-specific service rather than a traditional replaceable bulb.
The interior is predominantly LED as well, covering the dome, map, trunk, vanity, and step lights. The glove-box and general interior listings include 2825 and 98 bulb options. Verify the existing bulb or socket before ordering for those locations, since the applicable option can depend on the lamp assembly.