Consult your vehicle Owner's Manual or visit the GMC Certified Service experts at LaFontaine Buick GMC Lansing to be sure you get the proper oil for your vehicle. For 2011 or newer vehicles, dexos1™ Full Synthetic is the recommended oil specification (dexos1™ for gasoline engines, dexos2™ for light-duty diesel engines, 15W40 CJ-4 for Duramax diesel engines). Advantages of dexos1™ Full Synthetic over conventional motor oil include improved oil performance and protection, increased piston cleanliness, reduced oil consumption, and greater viscosity control.