Audi A4 Fog Light Bulb Size

Additional Notes

• The H11 bulb is the most frequently specified front fog light bulb across the Audi A4 lineup, covering model years 2007-2012 as well as 2002. It is a single-filament halogen bulb operating at 12V and 55W, built to the ECE standard with a PGJ19-2 base, and carries approval for use in the US market.
• The H8 bulb shares the same 12V and 35W operating values as several other halogen types in these specifications but draws notably less wattage than the H11 and H7 bulbs. It uses a PGJ19-1 base, which differs from the PGJ19-2 base of the H11, making the two physically incompatible despite their similar appearance.
• The H7, H8, and H11 bulbs all follow the ECE standard and carry US approval, yet each uses a distinct base type. H7 uses a PX26d base, H8 uses PGJ19-1, and H11 uses PGJ19-2. These differences mean none of the three are interchangeable with one another, even though H7 and H11 share the same 55W rating.
• The 921 bulb specified for the Audi A4 front fog lights in 2017-2018 represents a departure from the halogen ECE-standard bulbs used in all other listed years. It follows the ANSI standard common to the US and Canada, operates at 12V and 16W, and uses a wedge-style T15 fitting rather than a pin or bayonet base.
• The H1 bulb, specified for the 1996-1997 model years, uses a P14.5s single-pin base and operates at 12V and 55W. It holds ECE approval as well as approval in the US and Japan, but its base type is entirely distinct from all other halogen bulbs listed in these specifications.
• The rear fog light specifications reference the H21W bulb for the 2019-2020 Audi A4. Unlike the front fog light bulbs, the H21W is classified as a signalling bulb rather than a driving or passing lamp. It operates at 12V and 21W with a BAY9s bayonet base, and it follows the ECE standard.
• The 1999 Audi A4 front fog light specification carries two separate H7 entries, with one entry qualified by a VIN breakpoint at 8D-X-200 001. This indicates a mid-year production change, and the correct bulb selection for a 1999 model depends on where its VIN falls relative to that threshold.
• The H1 and H7 bulbs both operate at 12V and 55W and share approval in the US and Japan, yet they use entirely different base types. H1 uses a single-pin P14.5s base while H7 uses a two-pin PX26d base, so the two cannot be substituted for one another.
• Across the front fog light specifications, the operating voltage is 12V for every listed bulb type, which is consistent with standard 12-volt automotive electrical systems. Wattage, however, varies from 16W for the 921 up to 55W for the H7, H11, and H1 types.
• The 2019 rear fog light entry for the Audi A4 includes fitment qualifiers specifying halogen, inner position, without special body measures, standard design taillight assemblies. These conditions indicate that alternative configurations of the 2019 model may not share the same H21W specification.