If your vehicle has the 6.0L V8 engine (VIN Code U),use premium unleaded gasoline with a postedoctane rating of 91 or higher. You may also use regularunleaded gasoline rated at 87 octane or higher, butyour vehicle’s acceleration may be slightly reduced,and you may notice a slight audible knocking noise,commonly referred to as spark knock. If the octane isless than 87, you may notice a heavy knockingnoise when you drive. If this occurs, use a gasolinerated at 87 octane or higher as soon as possible.Otherwise, you might damage your engine. If you areusing gasoline rated at 87 octane or higher and youhear heavy knocking, your engine needs service.Gasoline SpecificationsAt a minimum, gasoline should meet ASTMspecification D 4814 in the United States orCAN/CGSB-3.5 in Canada. Some gasolines maycontain an octane-enhancing additive calledmethylcyclopentadienyl manganese tricarbonyl (MMT).General Motors recommends against the use ofgasolines containing MMT. See Additives onpage 5-6 for additional information.California FuelIf your vehicle is certified to meet California EmissionsStandards, it is designed to operate on fuels thatmeet California specifications. See the underhoodemission control label. If this fuel is not availablein states adopting California emissions standards,your vehicle will operate satisfactorily on fuels meetingfederal specifications, but emission control systemperformance may be affected. The malfunctionindicator lamp may turn on and your vehicle may faila smog-check test. See Malfunction Indicator Lampon page 3-41. If this occurs, return to your authorizedGM dealer for diagnosis. If it is determined that thecondition is caused by the type of fuel used, repairsmay not be covered by your warranty.AdditivesTo provide cleaner air, all gasolines in the United Statesare now required to contain additives that will helpprevent engine and fuel system deposits from forming,allowing your emission control system to workproperly. In most cases, you should not have to addanything to your fuel. However, some gasolines containonly the minimum amount of additive required tomeet U.S. Environmental Protection Agency regulations.5-6
