Otherwise, you could damage the engine. If heavyknocking is heard when using gasoline rated at87 octane or higher, the engine needs service.Gasoline SpecificationsAt a minimum, gasoline should meetASTM specification D 4814 in the United States orCAN/CGSB‐3.5 or 3.511 in Canada. Some gasolinescontain an octane-enhancing additive calledmethylcyclopentadienyl manganese tricarbonyl (MMT).We recommend against the use of gasolines containingMMT. See Additives on page 6‑6 for additionalinformation.California FuelIf the vehicle is certified to meet California EmissionsStandards, it is designed to operate on fuels that meetCalifornia specifications. See the underhood emissioncontrol label. If this fuel is not available in statesadopting California emissions standards, the vehiclewill operate satisfactorily on fuels meeting federalspecifications, but emission control system performancemight be affected. The malfunction indicator lamp couldturn on and the vehicle might fail a smog‐check test.See Malfunction Indicator Lamp on page 4‑55. If thisoccurs, return to your authorized dealer for diagnosis.If it is determined that the condition is caused by thetype of fuel used, repairs might not be covered by thevehicle 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 fuelinjectors and intake valves clean, or if the vehicleexperiences problems due to dirty injectors or valves,look for gasoline that is advertised as TOP TIERDetergent 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.6-6InformationProvidedby:
