Gasoline OctaneIf your vehicle has the 4.6L V8 engine (VINCode A), use premium unleaded gasoline with aposted octane rating of 91 or higher. You may alsouse regular unleaded gasoline rated at 87octane or higher, but your vehicle’s accelerationmay be slightly reduced, and you may noticea slight audible knocking noise, commonly referredto as spark knock. If the octane is less than 87,you may notice a heavy knocking noise when youdrive. If this occurs, use a gasoline rated at 87octane or higher as soon as possible. Otherwise,you might damage your engine. If you areusing gasoline rated at 87 octane or higher andyou hear heavy knocking, your engine needsservice.If your vehicle has the 4.4L V8 engine (VINCode D), use premium unleaded gasoline with aposted octane rating of 91 or higher. For bestperformance, use premium unleaded gasoline witha posted octane rating of 93. In an emergency,you can use regular unleaded gasoline with anoctane rating of 87 or higher. If 87 octane fuel isused, do not perform any aggressive drivingmaneuvers such as wide open throttle applications.You may also hear audible spark knock duringacceleration. Refill your tank with premium fuel assoon as possible to avoid damaging yourengine. If you are using gasoline rated at 91octane or higher and you hear 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 theuse of gasolines containing MMT. See Additiveson page 367 for additional information.366
