Service and Maintenance. . . 324The use of gasoline with anoctane rating lower than thatrecommended may cause engineknock. Continued use can causeengine damage and void thewarranty.If you detect a heavy engine knockeven when using a gasoline of therecommended octane rating, havethe engine checked. Short periodsof engine knock during hill climb-ing and acceleration are accept-able.To help keep fuel injectors andintake valves clean, see your dealerfor information about preventingdeposit-related problems.FUEL ADDITIVESGasoline should contain detergentadditives that will help preventengine and fuel system depositsfrom forming. Clean fuel injectorsand intake valves will allow youremission control system to workproperly. Some gasoline does notcontain sufficient quantities ofadditive to keep fuel injectors andintake valves clean. To make upfor this lack of detergency, it isrecommended that GM FuelSystem Treatment PLUS (GM partno. 88861011) be added to thefuel tank at every oil change orevery 15000 km, whichever occursfirst.Gasoline containing oxygenates,such as ethers and ethanol,may be available in your area.However, fuels containing morethan 10% ethanol, such as E-85(85% ethanol), or more than15% MTBE (an ether) should notbe used in vehicles that were notdesigned for those fuels.$10araCTS Page 324 Tuesday, September 15, 2009 12:30 PM
