GMPartsGiant.com offers the wholesale prices for genuine 2018 Buick LaCrosse parts. Parts like Engine Assembly-Manifold & Fuel Related Parts are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 4 Cyl 2.5L, 6 Cyl 3.6L. Model Code: 4 DOOR CX EXT NOTCHBACK, 4 DOOR CXL EXT NOTCHBACK, 4 DOOR CXS EXT NOTCHBACK.