If this occurs, use a gasoline rated at 87 octane orhigher as soon as possible. Otherwise, you coulddamage the engine. If heavy knocking is heard whenusing gasoline rated at 87 octane or higher, the engineneeds service.Gasoline SpecificationsAt a minimum, gasoline should meet ASTM specificationD 4814 in the United States or CAN/CGSB-3.5 or3.511 in Canada. Some gasolines contain anoctane-enhancing additive called methylcyclopentadienylmanganese tricarbonyl (MMT). We recommendagainst the use of gasolines containing MMT. SeeAdditives on page 6-6 for additional information.California FuelIf the 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, thevehicle will operate satisfactorily on fuels meeting federalspecifications, but emission control system performancemight be affected. The malfunction indicator lampcould turn on and the vehicle might fail asmog-check test.See Malfunction Indicator Lamp on page 4-57. If thisoccurs, return to your authorized dealer/retailer fordiagnosis. If it is determined that the condition is causedby the type of fuel used, repairs might not be coveredby the vehicle warranty.AdditivesTo provide cleaner air, all gasolines in the United Statesare now required to contain additives that help preventengine and fuel system deposits from forming, allowingthe emission control system to work properly. In mostcases, nothing should have to be added to the fuel.However, some gasolines contain only the minimumamount of additive required to meet U.S. EnvironmentalProtection Agency regulations. To help keep fuel injectorsand intake valves clean, or if the vehicle experiencesproblems due to dirty injectors or valves, look for gasolinethat is advertised as TOP TIER Detergent Gasoline.For customers who do not use TOP TIER DetergentGasoline regularly, one bottle of GM Fuel SystemTreatment PLUS, added to the fuel tank at everyengine oil change, can help clean deposits from fuelinjectors and intake valves. GM Fuel System TreatmentPLUS is the only gasoline additive recommended byGeneral Motors.Also, your dealer/retailer has additives that will helpcorrect and prevent most deposit-related problems.6-6
