For the 2018 Chevrolet Impala, headlight bulb fitment depends on the factory headlight type. Models with halogen headlights use a 9005 bulb for both the low beam and high beam. Models with HID headlights use a D3S bulb for both functions. The daytime running light also varies: halogen-equipped vehicles use 9005, while HID-equipped vehicles use LED.
Other notable exterior bulbs include 7444NA for the front turn signal and parking light, 7440 for the reverse light, and 7443R for the brake light. The center stop light is LED. Rear lighting uses several listed fitments: the tail light may use 194, 7441, or 7443R, while the rear turn signal uses 7443. Front and rear side markers use 194NA and 7443A, respectively. License plate lighting is listed with either 2825 or 98 bulbs. The glove box and trunk light listings include 194 and 7441. No fog light bulb fitment is listed in the supplied data.