For the 2015 Buick LaCrosse, the low- and high-beam bulb depends on the factory headlight system. Models with halogen headlights use a 9012 bulb for both low and high beam. Models equipped with HID headlights use a D3S bulb for both functions. Confirm the headlight type before ordering, since these bulbs are not interchangeable.
Daytime running light fitment also follows the headlight configuration: halogen-equipped models use 7443, while HID-equipped models use integrated LED lighting. The front turn signal and parking light use 7444NA, while the front side marker is 7443A with halogen headlights or LED with HID headlights.
Other useful replacements include 7440A rear turn signals and 921 reverse lights. The brake, center stop, tail, and rear side-marker lights are LED. License plate and several interior applications may use 2825 or 98; step, glove-box, and trunk locations may use 194 or 7441.