What Size Bulbs Does a 2018 Audi A4 Use?
Correct headlight, fog light, and tail light bulb sizes. Sourced from OEM catalog data.
Installation Difficulty
Hard (Tight clearances)
Est. Replacement Cost
$15 - $40 (Halogen) / $30+ (LED)
What Lighting System Does the 2018 Audi A4 Have?
The 2018 Audi A4 features a comprehensive lighting system with 9 bulb positions. It uses halogen technology with HID-D5S LED low beams and LED Headlights high beams in a dual-bulb configuration. The A4 has been available from 1996 to 2019, and the 2018 model falls in the late-generation years. As a Audi vehicle, it uses a CANbus electrical system that monitors bulb status.
LED Flicker Warning
This vehicle (Audi) is known to use a CANbus system that checks for burnt-out bulbs. Installing standard LEDs may cause them to flicker or trigger a dashboard error.
We highly recommend using a CANbus decoder or "Anti-Flicker" resistors.
Can You Put LED Bulbs in a 2018 Audi A4?
To upgrade the 2018 Audi A4 headlights to LED, you will need a HID-D5S LED LED kit for the low beams and a LED Headlights LED kit for the high beams. Start with the low beams since they are used most often and have the biggest impact on nighttime visibility. Important: Audi vehicles use a CANbus system that detects bulb wattage. Standard LED bulbs may trigger dashboard warnings or flicker. Choose LED kits labeled "CANbus-compatible" or add inline decoder resistors to prevent these issues. For the fog lights, a LED Fog Light LED bulb provides a clean white output that pairs well with LED headlights.
How to Replace Bulbs on a 2018 Audi A4
To remove the headlight bulb, disconnect the wiring harness, then twist the bulb counter-clockwise and pull it straight out of the housing. Audi vehicles are known for tight engine bay clearances around the headlight assembly. You may need to remove the air intake duct, battery cover, or wheel well liner to access the bulbs. Budget 30 to 45 minutes per side for your first replacement. When installing the new bulb, avoid touching the glass with bare fingers. Skin oils create hot spots that shorten bulb life. Wear clean gloves or handle the bulb by its plastic base only. The fog lights are accessed from underneath the front bumper. You may need to remove a few plastic clips or screws from the fender liner to reach the LED Fog Light fog light socket.
Full Upgrade Bundle
Upgrade All 10 Positions at Once
2018 Audi A4 Complete Bulb Size Chart
| Position | Bulb Size | Shop |
|---|---|---|
Low Beam | HID-D5S LED | Buy HID-D5S LED |
High Beam | LED Headlights | Buy LED Headlights |
Fog Light | LED Fog Light | Buy LED Fog Light |
Brake Light | Brake Light Assembly | Buy Brake Light Assembly |
Side Marker | LED Bulb | Buy LED Bulb |
Turn Signal Front | 12181NA | Buy 12181NA |
Parking Light | N/A | Buy N/A |
Turn Signal Rear | LED Bulb | Buy LED Bulb |
Reverse Light | LED Bulbs | Buy LED Bulbs |
Trunk Light | LED Light | Buy LED Light |
Want to upgrade everything at once?
Shop Complete LED Kit for 2018 Audi A4How Long Do 2018 Audi A4 Headlight Bulbs Last?
Standard halogen headlights on the 2018 Audi A4 have an expected lifespan of 500 to 1,000 hours, which works out to roughly 2 to 3 years of normal use. Signs of a failing halogen bulb include noticeably dimmer output, a yellowish tint compared to the other headlight, or intermittent flickering. At 8 years old, the original bulbs on your A4 are likely overdue for replacement. Even if they still illuminate, reduced brightness significantly impacts nighttime safety. When one headlight burns out, replace both sides at the same time. Bulbs from the same batch age at similar rates, and mismatched brightness is distracting to oncoming drivers.
What Bulbs Are Compatible with the 2018 Audi A4?
The D5S low beam bulb on the 2018 Audi A4 is a specific fitment. There are no widely recognized cross-compatible alternatives, so make sure to purchase the exact D5S size. Using the wrong bulb size can cause improper beam patterns that reduce your visibility and blind other drivers. It can also cause overheating inside the headlight housing, potentially warping the plastic lens or reflector. Always verify the bulb number before purchasing.
2018 Audi A4 Headlight FAQ
Did Audi A4 Bulb Sizes Change Over the Years?
Over its production run from 1996 to 2019, the Audi A4 has seen bulb size changes in the Low Beam, High Beam and Fog Light positions. The 2018 model uses the newer bulb specification introduced around 2017. Always verify the exact bulb size for your specific 2018 model year using the chart above, as using the wrong size can result in poor fitment or reduced light output.
Other A4 Years
More from Audi
Other Vehicles That Use HID-D5S LED Bulbs
These vehicles from other makes also use a HID-D5S LED low beam bulb: