GMPartsGiant.com offers the wholesale prices for genuine 2018 Cadillac ATS Sedan parts. Parts like Engine Assembly & Partial Engine 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 3.6L. Model Code: 4 DOOR LUXURY SEDAN, 4 DOOR PERFORMANCE SEDAN, 4 DOOR PREMIUM SEDAN, 4 DOOR SEDAN.