GMPartsGiant.com offers the wholesale prices for genuine 2018 Cadillac CT6 parts. Parts like Engine Oil Cooler And Lines are shipped directly from authorized GM dealers and backed by the manufacturer's warranty. Parts fit for the following vehicle options. Engine: 4 Cyl 2.0L, 6 Cyl 3.0L, 6 Cyl 3.6L. Model Code: 4 DOOR SEDAN, BASE 4 DOOR SEDAN, PLATINUM 4 DOOR SEDAN, PREMIUM 4 DOOR SEDAN.