If your vehicle has the 6.0L V8 engine(VIN Code U), use premium unleaded gasolinewith a posted octane rating of 91 or higher.You may also use regular unleaded gasolinerated at 87 octane or higher, but your vehicle’sacceleration may be slightly reduced, and you maynotice a slight audible knocking noise, commonlyreferred 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. Ifyou are using gasoline rated at 87 octane or higherand you hear heavy knocking, your engineneeds 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 336 for additional information.335
